Assistant to actor in clothing store (7)
I believe the answer is:
dresser
'assistant' is the definition.
(dresser is a kind of assistant)
'clothing store' is the wordplay.
'clothing' becomes 'dress' (dress is a kind of clothing).
'store' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'dress'+'er'='DRESSER'
'to actor in' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for dresser that I've seen before include "Theatre assistant" , "Sideboard; theatrical assistant" , "One who arranges" , "Piece of kitchen furniture" , "Sideboard - backstage assistant" .)