Puzzled birds in part of garden (7)
I believe the answer is:
bemused
'puzzled' is the definition.
(being bemused is being puzzled or confused)
'birds in part of garden' is the wordplay.
'birds' becomes 'emus' (emu is a kind of bird).
'in' means one lot of letters goes inside another.
'part of garden' becomes 'bed' (flower bed).
'emus' going inside 'bed' is 'BEMUSED'.
(Other definitions for bemused that I've seen before include "Lost for words" , "Dazed" , "Perplexed or absorbed in thought" , "Floored" , "Deep in thought" .)