Chaplain bringing a doctor into gym (5)
I believe the answer is:
padre
'chaplain' is the definition.
(I know that chaplain can be written as padre)
'a doctor into gym' is the wordplay.
'doctor' becomes 'Dr' (abbreviation).
'into' means one lot of letters goes inside another.
'gym' becomes 'pe' (short for Physical Education).
'a'+'dr'='adr'
'adr' placed within 'pe' is 'PADRE'.
'bringing' is the link.
(Other definitions for padre that I've seen before include "clerical worker" , "Priest, chaplain" , "Army serviceman?" , "Father" , "Sky pilot (military slang)" .)