Crossword Genius

Club supporter's leader that is supporting supporters (7)

Ross

I believe the answer is:

'club' is the definition.
(brassie is a kind of club)

'supporter's leader that is supporting supporters' is the wordplay.
'leader' suggests taking the first letters.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'supporters' becomes 'bras' (I've seen this in other clues).
The initial letter of 'supporters' is 's'.
's'+'ie'='sie'
'sie' after 'bras' is 'BRASSIE'.

(Other definitions for brassie that I've seen before include "Old golf club", "Golf-club", "Number two wood (golf)", "old wood".)

I've seen this clue in The Telegraph.