Bores the doctor with ailments (6)
I believe the answer is:
drills
'bores' is the definition.
(I've seen this before)
'doctor with ailments' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'with' means one lot of letters go next to another.
'ailments' becomes 'ills' ('ill' can be a synonym of 'ailment').
'dr'+'ills'='DRILLS'
'the' is the link.
(Other definitions for drills that I've seen before include "they bore" , "monkeys" , "Bores in army exercises" , "Trains, in military fashion" , "Teaches by repetition" .)