Short underclothes no good, but staying on (9)
I believe the answer is:
lingering
'staying on' is the definition.
(to linger is to hang around somewhere)
'short underclothes no good' is the wordplay.
'short' means to remove the last letter.
'underclothes' becomes 'lingerie' (lingerie is a kind of underclothes).
'no good' becomes 'ng' (abbreviation).
'lingerie' with its final letter removed is 'lingeri'.
'lingeri'+'ng'='LINGERING'
'but' is the link.
(Other definitions for lingering that I've seen before include "Reluctant to leave" , "Being slow to leave" , "Hanging back, tarrying" , "Being reluctant to part with" , "Remaining" .)