Doctor treating red guy is menial work (8)
I believe the answer is:
drudgery
'menial work' is the definition.
(I've seen this before)
'doctor treating red guy' is the wordplay.
'doctor' becomes 'Dr' (abbreviation).
'treating' indicates an anagram.
'red'+'guy'='redguy'
'redguy' is an anagram of 'udgery'.
'dr'+'udgery'='DRUDGERY'
'is' is the link.
(Other definitions for drudgery that I've seen before include "Grinding toil" , "Tedious toil" , "monotonous work" , "Dull menial work" , "Grind" .)