Obscene wife in jail (she confessed finally) (4)
I believe the answer is:
lewd
'obscene' is the definition.
(I've seen this before)
'wife in jail she confessed finally' is the wordplay.
'wife' becomes 'w'.
'in' is an insertion indicator.
'finally' suggests the final letters.
The last letters of 'jail she confessed' are 'led'.
'w' going into 'led' is 'LEWD'.
(Other definitions for lewd that I've seen before include "Sexually crude" , "Bawdy" , "Licentious or obscene" , "Dirty" , "Crude, offensive" .)