Implement found in garden for certain (7)
I believe the answer is:
enforce
'implement' is the definition.
('enforce' can be a synonym of 'implement')
'in garden for certain' is the wordplay.
'in' says the answer is hidden in the clue.
'ENFORCE' is hidden within 'garden for certain'.
'found' is the link.
(Other definitions for enforce that I've seen before include "Compel observation of" , "Compel compliance or obedience" , "Compel adherence to (a law)" , "Impose with power" , "Compel or impose obedience, say to law" .)