State imprisoning upper-class caught being impudent (5)
I believe the answer is:
saucy
'being impudent' is the definition.
(synonyms)
'state imprisoning upper-class caught' is the wordplay.
'state' becomes 'say' (speak).
'imprisoning' indicates putting letters inside.
'upper class' becomes 'u' (as in U- and non-U speech).
'caught' becomes 'c' (cricket abbreviation).
'u'+'c'='uc'
'say' placed around 'uc' is 'SAUCY'.
(Other definitions for saucy that I've seen before include "Cheeky, impertinent" , "Risque" , "Cheeky; risquZ" , "Impertinent - jaunty" , "Pert and toothsome" .)