Gift had teacher worried (6)
I believe the answer is:
donate
'gift' is the definition.
(donating is a kind of gifting)
'teacher worried' is the wordplay.
'teacher' becomes 'don' (don is a kind of teacher).
'worried' becomes 'ate' (something worrying may eat someone up).
'don'+'ate'='DONATE'
'had' acts as a link.
(Other definitions for donate that I've seen before include "give in kindness" , "Make a contribution" , "Give (money) to a good cause" , "Contribute charitably" , "Give - present" .)