Idler having answer in amateur contest (8)
I believe the answer is:
layabout
'idler' is the definition.
('layabout' can be a synonym of 'idler')
'answer in amateur contest' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'in' means one lot of letters goes inside another.
'amateur' becomes 'lay' ('lay' can be similar in meaning to 'amateur'**).
'contest' becomes 'bout' (I've seen this in other clues).
'lay'+'bout'='laybout'
'a' placed inside 'laybout' is 'LAYABOUT'.
'having' acts as a link.
(Other definitions for layabout that I've seen before include "wastrel" , "good-fornothing" , "Idler" , "Unemployed person" , "Lazy person" .)