Brown shirt, odd fit (7)
I believe the answer is:
tantrum
'fit' is the definition.
('tantrum' can be a synonym of 'fit')
'brown shirt odd' is the wordplay.
'brown' becomes 'tan' (tan is a kind of brown).
'shirt' becomes 't' (as in a T-shirt).
'odd' becomes 'rum' (I've seen this before).
'tan'+'t'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Child's outburst of bad temper" , "Pet, temper" , "Childish outbreak of temper" , "Display of bad temper" , "Burst of temper" .)