Head returns carrying uniform giving look of displeasure (4)
I believe the answer is:
pout
'look of displeasure' is the definition.
(I've seen this in another clue)
'head returns carrying uniform' is the wordplay.
'head' becomes 'top' (synonyms).
'returns' shows that the letters should be reversed in order.
'carrying' indicates putting letters inside.
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'top' written backwards gives 'pot'.
'pot' going around 'u' is 'POUT'.
'giving' acts as a link.
(Other definitions for pout that I've seen before include "show sulkiness" , "Petulant look; fish" , "prepare for selfie?" , "Push lips out as sign of annoyance" , "Push out the lips (alluringly?)" .)