Recognise, tell apart (7)
I believe the answer is:
discern
I believe this clue is a double definition.
'recognise' is the first definition.
(synonyms)
'tell apart' is the second definition.
(synonyms)
(Other definitions for discern that I've seen before include "Espy" , "Recognise, find out" , "Perceive - distinguish" , "spot" , "Notice" .)