Breaking the rules, the doctor goes in for a rest (7)
I believe the answer is:
slumber
'for a rest' is the definition.
(I have seen 'The rest' mean 'slumber' so perhaps 'rest' could also mean 'slumber')
'breaking the rules the doctor goes in' is the wordplay.
'breaking' indicates anagramming the letters.
'the doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'goes in' indicates putting letters inside.
'rules' is an anagram of 'sluer'.
'sluer' going around 'mb' is 'SLUMBER'.
(Other definitions for slumber that I've seen before include "nap" , "Snooze" , "snores, maybe?" , "Rumbles (anag.)" , "Doze" .)