Possess topless robe (3)
I believe the answer is:
own
'possess' is the definition.
(I know that possess can be written as own)
'topless robe' is the wordplay.
'topless' means to remove the first letter.
'robe' becomes 'gown' (synonyms).
'gown' with its first letter removed is 'OWN'.
(Other definitions for own that I've seen before include "Acknowledge" , "Keep" , "Private" , "Control" , "Be in legal possession of (3)" .)