  PSR J1012$-$4235 is a 3.1ms pulsar in a wide binary (37.9 days) with a white
dwarf companion. We detect, for the first time, a strong relativistic Shapiro
delay signature in PSR J1012$-$4235. Our detection is the result of a timing
analysis of data spanning 13 years and collected with the Green Bank, Parkes,
and MeerKAT Radio Telescopes and the Fermi $\gamma$-ray space telescope. We
measured the orthometric parameters for Shapiro delay and obtained a 22$\sigma$
detection of the $h_{\rm 3}$ parameter of 1.222(54) $\mu$s and a 200$\sigma$
detection of $\varsigma$ of 0.9646(49). With the assumption of general
relativity, these measurements constrain the pulsar mass ($M_{\rm
p}=1.44^{+0.13}_{-0.12}$M$_{\odot}$), the mass of the white dwarf companion
($M_{\rm c} = 0.270^{+0.016}_{-0.015}$M$_{\odot}$ ), and the orbital
inclination ($i=88.06^{+0.28}_{-0.25} \deg$). Including the early $\gamma$-ray
data in our timing analysis facilitated a precise measurement of the proper
motion of the system of 6.58(5) mas yr$^{-1}$. We also show that the system has
unusually small kinematic corrections to the measurement of the orbital period
derivative, and therefore has the potential to yield stringent constraints on
the variation of the gravitational constant in the future.
