Unfriendly old fellow and school member (6)

I believe the answer is:

offish

'unfriendly' is the definition.
(offish can mean aloof or unfriendly)

'old fellow and school member' is the wordplay.
'old' becomes 'o' (abbreviation).
'fellow' becomes 'f' (abbreviation - of a society etc.).
'and' is a charade indicator (letters next to each other).
'school member' becomes 'fish' (school can mean a group of fish).
'o'+'f'+'fish'='OFFISH'

(Another definition for offish that I've seen is " Aloof, distant in manner".)

I've seen this clue in The Guardian.

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