Wants trousers but no top (5)
I believe the answer is:
lacks
'wants' is the definition.
('lack' can be a synonym of 'want')
'trousers but no top' is the wordplay.
'trousers' becomes 'slacks' (type of trousers).
'but no top' means to remove the first letter (the letter at the top is removed).
'slacks' with its initial letter removed is 'LACKS'.
(Other definitions for lacks that I've seen before include "Is without, wants" , "Wants, is deficient in" , "Doesn't have" , "Needs" , "Has a want" .)