Cheaper attire falling apart after short time (7)
I believe the answer is:
Here is my best explanation:
'cheaper' is the definition.
('tatty' can be a synonym of 'cheap')
'attire falling apart after short time' is the subsidiary indication.
'falling apart' indicates an anagram.
'after' means one lot of letters go next to another.
'short time' becomes 't' (abbreviation for time**).
'attire' with letters rearranged gives 'attier'.
'attier' put after 't' is 'tattier'.
(Another definition for tattier that I've seen is "More shabby".)