Wife having new zip to open dress (4)
I believe the answer is:
gown
'dress' is the definition.
(I know that gown is a kind of dress)
'wife having new zip to open' is the wordplay.
'wife' becomes 'w' (abbreviation).
'having' is a charade indicator (letters next to each other).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'zip' becomes 'go' (both can mean energy or enthusiasm).
'to open' means one lot of letters go next to another (some letters go before or 'open' others).
'w'+'n' is 'wn'.
'wn' put after 'go' is 'GOWN'.
(Other definitions for gown that I've seen before include "Loose dress or robe" , "Woman's long dress or judge's robe" , "Dress for formal occasions" , "Loose flowing garment for woman or judge" , "Academic attire" .)