Gets toupee in case of thinness (5)
I believe the answer is:
twigs
'gets' is the definition.
The definition and answer can be both related to change as well as being verbs in their -s form.
Maybe you can see an association between them that I don't see?
'toupee in case of thinness' is the wordplay.
'toupee' becomes 'wig' (a toupee is a wig).
'in' indicates putting letters inside.
'case of' suggests removing the centre (outsides of).
'thinness' with its middle taken out is 'ts'.
'wig' placed into 'ts' is 'TWIGS'.
Can you help me to learn more?
(Other definitions for twigs that I've seen before include "Catches on" , "Kindling" , "Slender (tree) shoots" , "Understands" , "Small branches" .)