Saying a team must keep two metres apart (5)
I believe the answer is:
maxim
'saying' is the definition.
(maxim is a kind of saying)
'a team must keep two metres apart' is the wordplay.
I cannot quite see how this works, but
'a' is present in the answer.
'team' could be 'xi' (eleven, a football team) and 'xi' is found within the answer.
'metres' could be 'm' and 'm' is present in the answer.
A single letter 'm' remains 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 maxim that I've seen before include "General rule" , "Saw - type of gun" , "Apophthegm" , "Gorky saw" , "Short pithy saying" .)