Relative triumph, finally, with American pop group? (7)
I believe the answer is:
husband
'relative' is the definition.
(I know that husband is a type of spouse)
'triumph finally with american pop group?' is the wordplay.
'finally' indicates one should take the final letters.
'with' means one lot of letters go next to another.
'american' becomes 'US' (United States).
'pop group?' becomes 'band' (I've seen this before).
The last letter of 'triumph' is 'h'.
'h'+'us'+'band'='HUSBAND'
(Other definitions for husband that I've seen before include "Partner in marriage" , "Woman's matrimonial partner" , "Partner; use carefully" , "be economical" , "manage carefully" .)