Flyer told to pay for uniform? (7)
I believe the answer is:
biplane
'flyer' is the definition.
(biplane is a kind of aircraft)
'told to pay for uniform?' is the wordplay.
'told' indicates a 'sounds like' (homophone) clue.
'to pay for' becomes 'buy' (I've seen this in another clue).
'uniform?' becomes 'plane' (both can mean even or flat).
'buy' is a homophone of 'bi'.
'bi'+'plane'='BIPLANE'
(Other definitions for biplane that I've seen before include "Eg, Tiger Moth" , "craft" , "Early aircraft" , "flying machine" , "Old aircraft" .)