A garden implement piercing pet bird (8)
I believe the answer is:
parakeet
'bird' is the definition.
(parakeet is a kind of bird)
'a garden implement piercing pet' is the wordplay.
'garden implement' becomes 'rake' (I've seen this before).
'piercing' is an insertion indicator (some letters pierce a hole in others).
'a'+'rake'='arake'
'arake' put within 'pet' is 'PARAKEET'.
(Other definitions for parakeet that I've seen before include "Tropical bird" , "Small long-tailed parrot" , "Small long-tailed bird" , "Bird popular as a pet" , "Take pear (anag) - bird" .)