Stay with me, sweetheart, in underwear (8)
I believe the answer is:
lingerie
'underwear' is the definition.
(type of underwear)
'stay with me sweetheart' is the wordplay.
'stay' becomes 'linger' (lingering is a kind of staying).
'with' means one lot of letters go next to another.
'me' becomes 'I'.
'sweetheart' becomes 'e' (the middle letter or heart of 'sweet').
'linger'+'i'+'e'='LINGERIE'
'in' is the link.
(Other definitions for lingerie that I've seen before include "Women's flimsy underwear" , "Female underwear" , "Women's underwear and nightwear" , "frillies" , "Ladies' underwear" .)