Put on some headdress (3)
I believe the answer is:
add
'put on' is the definition.
(as in adding something on)
'some headdress' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'ADD' can be found hidden inside 'headdress'.
(Other definitions for add that I've seen before include "Include" , "Say as a further remark" , "Tot; append" , "Count up" , "Contribute" .)