Clap Purviance, unevenly acting like a goat (7)
I believe the answer is:
caprine
'acting like a goat' is the definition.
(caprine means like a goat)
'clap purviance unevenly' is the wordplay.
'unevenly' indicates alternate letters (letters in odd-numbered positions rather than even).
'clap'+'purviance'='clappurviance'
The alternate letters of 'clappurviance' are 'CAPRINE'.
(Other definitions for caprine that I've seen before include "acting the goat?" , "Goat-like" .)