  We present the N-band (8-13 micron) spectrum of the hidden compact radio
super-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6m
telescope. The spectrum is characterised by a rising continuum due to warm
dust, a silicate absorption and a strong [SIV] line at 10.5 micron. Weaker
lines of [ArIII] at 9.0 micron and [NeII] at 12.8 micron are also present. The
continuum can be modeled by an optically thick emission from hot dust emission
extinguished by a cold foreground dust screen and a silicate absorption feature
with A_sil = 0.73+/-0.05 mag. We show how the spatial scale of the observations
greatly determine the mid-IR appearance of NGC 5253 and the important
implications that this has on the interpretation of line fluxes in terms of the
properties (age, IMF, etc.) of the embedded cluster. We have modeled the
observed line fluxes towards C2 using photoionisation models with the most
recent spectral energy distributions available to describe the integrated
properties of the stellar cluster. Strong constraints on the geometry based on
high spatial resolution observations at different wavelengths -- near-IR (HST
and Keck), mid-IR (TIMMI2) and radio (VLA) -- allows us to restrain the
ionisation parameters to values logU >= -0.5 dex. This constraint on U lead to
two possible solutions for the age and upper mass cutoff of C2: 1) a young (< 4
Myr) cluster with a "non-standard" IMF with a low upper mass cutoff Mup < 50
Msun, and 2) a cluster of ~5-6 Myr with a standard high upper mass cutoff (Mup
\~ 100 Msun). Arguments in favour and against these two scenarios are
presented. The origin of the [OIV] 25.9 micron emission measured by ISO and the
possible presence of an intermediate mass black hole inside C2 are also
addressed.
