more slight (7)
I believe the answer is:
slimmer
'more slight' is the definition.
('slim' can be a synonym of 'slight')
This is the entire clue.
(Other definitions for slimmer that I've seen before include "I aim to get rid of some" , "More slender" , "More slenderly built" , "with less fat" , "One attempting to lose weight" .)