A doctor backed probing boozer’s guts (7)
I believe the answer is:
innards
'guts' is the definition.
(thesaurus)
'a doctor backed probing boozer's' is the wordplay.
'doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor'**).
'backed' says the letters should be written backwards.
'probing' indicates putting letters inside (probe can mean to make a hole in).
'boozer's' becomes 'inns'.
'dr' back-to-front is 'rd'.
'a'+'rd'='ard'
'ard' inserted into 'inns' is 'INNARDS'.
(Other definitions for innards that I've seen before include "Most of haggis" , "Insides" , "Informal intestines and organs" , "Informally, stomach and bowels" , "Guts of mechanism" .)