Redgrave perhaps first in rehearsal after argument with European (5)
I believe the answer is:
rower
'redgrave' is the definition.
(Steve Redgrave is an Olympic rower)
'first in rehearsal after argument with european' is the wordplay.
'first in rehearsal' becomes 'r' (1st letter of 'rehearsal').
'after' says to put letters next to each other.
'argument' becomes 'row' (to row is to argue).
'with' says to put letters next to each other.
'european' becomes 'E' (abbreviation e.g. EU).
'row'+'e'='rowe'
'r' put after 'rowe' is 'ROWER'.
'perhaps' is the link.
(Other definitions for rower that I've seen before include "Maybe one in eight" , "One in eight, perhaps" , "one pulling a blade?" , "Oarsman/woman" , "Oarsman (or woman)" .)