Side of the hollow — a metre (4)
I believe the answer is:
team
'side' is the definition.
(a side is a sporting team)
'the hollow a metre' is the wordplay.
'hollow' suggests removing the centre (the word is hollowed out).
'metre' becomes 'm' (synonyms).
'the' with its centre taken out is 'te'.
'te'+'a'+'m'='TEAM'
'of' is the link.
(Other definitions for team that I've seen before include "Squad; side" , "Side in sporting event" , "Side; match" , "Two or more working together" , "See 22" .)