Doctor Steed called in in Split (9)
I believe the answer is:
estranged
'split' is the definition.
(I've seen this before)
'doctor steed called in' is the wordplay.
'doctor' indicates anagramming the letters.
'called' becomes 'rang' (called on the phone).
'in' means one lot of letters goes inside another.
'steed' with letters rearranged gives 'ested'.
'ested' placed around 'rang' is 'ESTRANGED'.
'in' acts as a link.
(Other definitions for estranged that I've seen before include "no longer friendly" , "A nerd gets (anag) - separated" , "Split" , "Alienated, disaffected" , "Sad regent (anag) - disaffected" .)