Celtic fan, perhaps, sawing a leg off (10)
I believe the answer is:
glaswegian
'celtic fan' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'sawing a leg off' is the wordplay.
'off' is an anagram indicator.
'sawing'+'a'+'leg'='sawingaleg'
'sawingaleg' anagrammed gives 'GLASWEGIAN'.
'perhaps' is the link.
Can you help me to learn more?
(Other definitions for glaswegian that I've seen before include "Scotsman" , "Scot" , "Celt?" .)