Desire seeing topless hag! (4)
I believe the answer is:
itch
'desire' is the definition.
(itch is a kind of desire)
'topless hag' is the wordplay.
'topless' means to remove the first letter.
'hag' becomes 'witch' ('witch' can be a synonym of 'hag').
'witch' with its initial letter removed is 'ITCH'.
'seeing' is the link.
(Other definitions for itch that I've seen before include "Restless longing" , "are dying" , "Impatient desire (colloq.)" , "Tickling sensation of skin" , "It needs scratching" .)