Independent enterprise cancelling head's contract (9)
I believe the answer is:
indenture
'contract' is the definition.
(I know that indenture is a type of contract)
'independent enterprise cancelling head's' is the wordplay.
'independent' becomes 'ind' (politics abbreviation).
'enterprise' becomes 'venture' (I've seen this in another clue).
'cancelling head' means to remove the first letter.
'venture' with its initial letter taken away is 'enture'.
'ind'+'enture'='INDENTURE'
(Other definitions for indenture that I've seen before include "Agreement binding apprentice to a master" , "Document" , "served by a novice?" , "Sealed agreement" , "contract" .)