Decide to put off excavation (9)
I believe the answer is:
determine
'decide' is the definition.
(I know that decide can be written as determine)
'put off excavation' is the wordplay.
'put off' becomes 'deter' (both can mean to discourage).
'excavation' becomes 'mine' (mine is a kind of excavation).
'deter'+'mine'='DETERMINE'
'to' is the link.
(Other definitions for determine that I've seen before include "Choose" , "Firmly decide" , "Decide - to settle" , "Learn" , "conclusion" .)