In the photograph I spotted a garden pest (5)
I believe the answer is:
aphis
'a garden pest' is the definition.
(I've seen this before)
'in the photograph i spotted' is the wordplay.
'in' indicates the answer is hidden within the clue.
'APHIS' can be found hidden inside 'photograph i spotted'.
(Other definitions for aphis that I've seen before include "Sap-sucking garden pest" , "sucker?" , "Small insect" , "Greenfly" , "Plant louse" .)