Yellowish-brown shirt, odd fit (7)
I believe the answer is:
tantrum
'fit' is the definition.
(I know that fit can be written as tantrum)
'yellowish-brown shirt odd' is the wordplay.
'yellowish-brown' becomes 'tan' (yellowish-brown colour).
'shirt' becomes 't' (as in a T-shirt).
'odd' becomes 'rum' (rum can mean strange or dubious).
'tan'+'t'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Child's outburst of bad temper" , "Display of bad temper" , "Burst of rage" , "fit of bad temper" , "Wobbly" .)