He gets publicity for principals (5)
I believe the answer is:
heads
'for principals' is the definition.
('head' can be a synonym of 'principal')
'he gets publicity' is the wordplay.
'he' becomes 'hes' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gets' indicates putting letters inside (gets can mean captures or absorbs).
'publicity' becomes 'ad' (short for advertisement).
'hes' placed around 'ad' is 'HEADS'.
Can you help me to learn more?
(Other definitions for heads that I've seen before include "Goes for" , "Noddles; nuts" , "Coin-tossing call" , "Leaders" , "School principals" .)