A long time out in town getting a dress (3,4)
I believe the answer is:
tea gown
'a dress' is the definition.
(tea gown is a kind of dress)
'a long time out in town' is the wordplay.
'long time' becomes 'eg' (I can't justify this - if you can you should believe this answer much more).
'out' means one lot of letters goes inside another.
'in' means one lot of letters goes inside another.
'a' placed into 'eg' is 'eag'.
'eag' put within 'town' is 'TEA-GOWN'.
'getting' is the link.
Can you help me to learn more?
(Other definitions for tea gown that I've seen before include "Loose garment" , "party dress" .)