A role that’s separate (5)
I believe the answer is:
apart
'separate' is the definition.
(similar in meaning)
'a role' is the wordplay.
'role' becomes 'part' (synonyms).
'a'+'part'='APART'
'that's' is the link.
(Other definitions for apart that I've seen before include "In pieces; separate" , "set aside" , "Independently" , "(Break) into pieces" , "First Christmas present from my love" .)