Reckless and demented headwear (6)
I believe the answer is:
madcap
'reckless' is the definition.
(I've seen this in another clue)
'demented headwear' is the wordplay.
'demented' becomes 'mad' (synonyms).
'headwear' becomes 'cap' (cap is a type of hat).
'mad'+'cap'='MADCAP'
'and' acts as a link.
(Other definitions for madcap that I've seen before include "Given to reckless behaviour" , "Oddball" , "Foolhardy" , "Foolish, reckless" , "Hothead" .)