Senior member of college tumbled over wicket (6)
I believe the answer is:
fellow
'senior member of college' is the definition.
(member of a university college)
'tumbled over wicket' is the wordplay.
'tumbled' becomes 'fell' (to tumble is to fall over).
'over' becomes 'o' (cricket abbreviation).
'wicket' becomes 'w'.
'fell'+'o'+'w'='FELLOW'
(Other definitions for fellow that I've seen before include "Companion or associate" , "The other of a pair - just a chap" , "The other of a pair, or a college member" , "Academic chap?" , "Comrade" .)