Unsympathetic to one new patient (10)
I believe the answer is:
intolerant
'unsympathetic' is the definition.
(thesaurus)
'one new patient' is the wordplay.
'one new' becomes 'in' (I've seen this in other clues).
'patient' becomes 'tolerant' ('tolerant' can be similar in meaning to 'patient').
'in'+'tolerant'='INTOLERANT'
'to' acts as a link.
(Other definitions for intolerant that I've seen before include "Lacking respect for the beliefs of others" , "Bigoted" , "Impatient" , "illiberal" , "Hating" .)