Get thinner and lighter (5)
I believe the answer is:
taper
I believe this is a double definition.
'get thinner' is the first definition.
(I've seen this before)
'lighter' is the second definition.
(I've seen this before)
'and' acts as a link.
(Other definitions for taper that I've seen before include "Give a point" , "See the light" , "Narrow towards the end" , "Fall off" , "recording artist" .)