Usual fellow providing excuse (6)
I believe the answer is:
pardon
'excuse' is the definition.
(I know that excuse can be written as pardon)
'usual fellow' is the wordplay.
'usual' becomes 'par' (par is an average golf score).
'fellow' becomes 'don' (both can mean an academic).
'par'+'don'='PARDON'
'providing' is the link.
(Other definitions for pardon that I've seen before include "Allow to go unpunished" , "indulgence" , "Ask this to seek forgiveness" , "Grant forgiveness" , "Polite expression of regret, please excuse" .)