Resting during performance, wives will be undressed (8)
I believe the answer is:
inactive
'resting' is the definition.
(I've seen this before)
'during performance wives will be undressed' is the wordplay.
'during' becomes 'in' (I've seen this in other clues).
'performance' becomes 'act' (act is a kind of performance).
'will be undressed' means to look at the middle letters (outside letters which clothe the word are removed).
The centre of 'wives' is 'ive'.
'in'+'act'+'ive'='INACTIVE'
(Other definitions for inactive that I've seen before include "Dormant" , "Still" , "Having no effect" , "Quiescent" , "Not doing anything, passive" .)