Garden rubbish hazard (6)
I believe the answer is:
danger
'hazard' is the definition.
(thesaurus)
'garden rubbish' is the wordplay.
'rubbish' indicates anagramming the letters.
'garden' is an anagram of 'DANGER'.
(Other definitions for danger that I've seen before include "Red flag, for example" , "Peril, hazard" , "Peril, threat" , "Peril in garde" , "Peril, exposure to harm" .)