Head off to bury pet smashed by front of car (9)
I believe the answer is:
intercept
'head off' is the definition.
'bury pet smashed by front of car' is the wordplay.
'bury' becomes 'inter' (I've seen this before).
'smashed' is an anagram indicator.
'by' means one lot of letters go next to another.
'front of' indicates taking the first letters.
The initial letter of 'car' is 'c'.
'pet' anagrammed gives 'ept'.
'ept' after 'c' is 'cept'.
'inter'+'cept'='INTERCEPT'
'to' is the link.
(Other definitions for intercept that I've seen before include "Obstruct to prevent reaching a destination" , "Successfully hit (target with missile)" , "cut off" , "Head off; ambush" , "point on graph" .)