Common weed partly spoilt row, gardener recalled (7)
I believe the answer is:
ragwort
'common weed' is the definition.
'partly spoilt row gardener recalled' is the wordplay.
'partly' says the answer is hidden in the clue.
'recalled' says the letters should be written in reverse.
'trowgar' can be found hidden inside 'spoilt row gardener'.
'trowgar' in reverse letter order is 'RAGWORT'.
(Other definitions for ragwort that I've seen before include "Plant toxic to livestock" , "I'm toxic to livestock" , "Yellow flower, poisonous to cattle" , "Widespread obnoxious weed" , "Yellow-flowered weed" .)