Queue behind rugby player (8)
I believe the answer is:
tailback
'queue' is the definition.
(I have seen 'Queue of cars ' mean 'tailback' so perhaps 'queue' could also mean 'tailback')
'behind rugby player' is the wordplay.
'behind' becomes 'tail' (synonyms).
'rugby player' becomes 'back' (type of rugby player).
'tail'+'back'='TAILBACK'
(Other definitions for tailback that I've seen before include "delayed traffic" , "Long queue of traffic" , "Queue of cars" , "Sort of jam" , "Traffic jam" .)