Small talk primarily concerning manufacturer of headgear (7)
I believe the answer is:
chatter
'small talk' is the definition.
(I've seen this before)
'primarily concerning manufacturer of headgear' is the wordplay.
'primarily' suggests taking the first letters.
'manufacturer of headgear' becomes 'hatter' (someone who makes hats).
The initial letter of 'concerning' is 'c'.
'c'+'hatter'='CHATTER'
(Other definitions for chatter that I've seen before include "Small talk" , "Gas" , "Rabbit on" , "Trivial conversation" , "Insignificant talk" .)