Feast for head of physics in small study (6)
I believe the answer is:
spread
'feast' is the definition.
(I know that feast can be written as spread)
'head of physics in small study' is the wordplay.
'head of' says to take the initial letters.
'in' indicates putting letters inside.
'small' becomes 's' (abbreviation - e.g. clothes size).
'study' becomes 'read' (synonyms).
The initial letter of 'physics' is 'p'.
's'+'read'='sread'
'p' going within 'sread' is 'SPREAD'.
'for' is the link.
(Other definitions for spread that I've seen before include "Expanse; edible paste" , "Unfold - scatter" , "Stretch out; big meal" , "Open, fan out, unfold" , "Distribute or disperse widely" .)