We had reported garden intruder (4)
I believe the answer is:
weed
'garden intruder' is the definition.
(I've seen this in another clue)
'we had reported' is the wordplay.
'we had' becomes 'we'd' (contraction of 'we had').
'reported' shows a homophone (sound like).
'wed' sounds like 'WEED'.
(Other definitions for weed that I've seen before include "Uncultivated plant" , "Got rid of water" , "Marijuana (slang)" , "gone!" , "Wild unwanted plant - tobacco?" .)