Clean up raised garden, huge, he's ignored (5)
I believe the answer is:
debug
'clean up' is the definition.
(to debug is to resolve a computer error)
'raised garden huge he's ignored' is the wordplay.
'raised' says the letters should be written in reverse (going up in a down clue).
'garden' becomes 'bed' (I've seen this in other clues).
'ignored' indicates named letters should be taken away.
'bed' backwards is 'deb'.
'huge' with 'he' removed is 'ug'.
'deb'+'ug'='DEBUG'
(Other definitions for debug that I've seen before include "Fix (program) errors" , "put things right" , "Remove (software) errors" , "correct code?" , "Fix computer program problems" .)