The peril of the garden (6)
I believe the answer is:
danger
'the peril' is the definition.
('danger' can be a synonym of 'peril')
'of the garden' is the wordplay.
'of' is an anagram indicator (the answer comes from or 'of' the letters).
'garden' anagrammed gives 'DANGER'.
(Other definitions for danger that I've seen before include "Peril in garde" , "Red flag, for example" , "Peril, hazard" , "'Peril, risk (6)'" , "Garden (anag) - peril" .)