Player in cricket side is behind doctor dressed in red (10)
I believe the answer is:
trombonist
'player' is the definition.
(trombone player)
'cricket side is behind doctor dressed in red' is the wordplay.
I cannot quite understand how this works, but
'side' could be 'r' (abbreviation for right) and 'r' is found in the answer.
'is' is present in the answer.
'doctor' could be 'mb' (Bachelor of Medicine, Medicinae Baccalaureus) and 'mb' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'in' acts as a link.
(Other definitions for trombonist that I've seen before include "Brass player" , "Ted Heath, perhaps" .)