Shows off scarves and shirts (6)
I believe the answer is:
boasts
'shows off' is the definition.
Although both the answer and definition are verbs in their -s form, I don't see how they can define each other.
'scarves and shirts' is the wordplay.
'scarves' becomes 'boas' (boa is a kind of scarf).
'and' means one lot of letters go next to another.
'shirts' becomes 'ts' (I can't justify this - if you can you should give a lot more credence to this answer).
'boas'+'ts'='BOASTS'
Can you help me to learn more?
(Other definitions for boasts that I've seen before include "Brags, shows off" , "Brags, blows" , "Brags in praise of oneself" , "crows" , "Blows one's own trumpet" .)