Sleeveless garment worn by only child, perhaps (9)
I believe the answer is:
singleton
'only child perhaps' is the definition.
I can't tell whether this definition defines the answer.
'sleeveless garment worn' is the wordplay.
'sleeveless garment' becomes 'singlet' (I've seen this before).
'worn' becomes 'on' (as in having clothes on).
'singlet'+'on'='SINGLETON'
'by' is the link.
Can you help me to learn more?
(Other definitions for singleton that I've seen before include "lonely heart, perhaps" , "One club maybe" , "in club, maybe, all alone" , "Anything on its own" , "One object only" .)