Just a fraction of a Rugby team (5-8)
I believe the answer is:
three-quarters
'just a' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'fraction of a rugby team' is the wordplay.
I cannot quite understand how this works, but
'fraction' could be 'quarter' (quarter is a kind of fraction) and 'quarter' is found within the answer.
The remaining letters 'threes' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for three-quarters that I've seen before include "Rugby line" , "75 per cent" .)