Long-suffering (4)
'long-suffering' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for patient that I've seen before include "doctor's client" , "One in hospital" , "Doctor's 'customer'" , "Long-suffering - person in hospital" , "one receiving medical treatment" .)
I believe this clue is a double definition.
'long' is the first definition.
(to long for something is to ache for it)
'suffering' is the second definition.
(I've seen this before)
(Other definitions for ache that I've seen before include "Feel pain" , "burn" , "Long ? pain" , "Hanker" , "Persistent dull pain" .)