Groom wanting old band (5)
I believe the answer is:
combo
'band' is the definition.
(combo is a kind of band)
'groom wanting old' is the wordplay.
'groom' becomes 'comb' (combing is a kind of grooming).
'wanting' is a charade indicator (letters next to each other).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'comb'+'o'='COMBO'
(Other definitions for combo that I've seen before include "Small (jazz or rock) band" , "Small pop group" , "group of players" , "Small jazz group" , "Music group" .)