Fifth shirt and jumper, say? (3,4)
I believe the answer is:
top gear
'fifth' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'shirt and jumper say?' is the wordplay.
'shirt' becomes 'top' (I've seen this in another clue).
'and' is a charade indicator (letters next to each other).
'jumper say?' becomes 'gear' (I can't explain this - if you can you should give a lot more credence to this answer).
'top'+'gear'='TOP GEAR'
Can you help me to learn more?
(Other definitions for top gear that I've seen before include "Best clobber" , "Finest clothes" , "Fashion" , "series on TV" , "One cruises in this" .)