Dull colour of an old uniform (3)
I believe the answer is:
dun
'dull colour' is the definition.
'dun' can be an answer for 'colour' (dun is a kind of colour). I am not sure about the 'dull' bit.
'of an old uniform' is the wordplay.
'of' indicates the answer is hidden within the clue.
'DUN' is hidden in the letters of 'old uniform'.
Can you help me to learn more?
(Other definitions for dun that I've seen before include "Brownish grey horse" , "Pursue or badger for debt" , "Press for payment" , "press for money" , "Demand for money" .)