In the light, wife is off colour (4)
I believe the answer is:
lewd
'off colour' is the definition.
(as in a lewd remark)
'in the light wife' is the wordplay.
'in' means one lot of letters goes inside another.
'the light' becomes 'led' (I've seen this before).
'wife' becomes 'w'.
'led' placed around 'w' is 'LEWD'.
'is' is the link.
(Other definitions for lewd that I've seen before include "Indecent and vulgar (4)" , "Sexually crude" , "Obscene, indecent" , "Smutty" , "Obscene - lustful - sensual" .)