Left a person without company (4)
I believe the answer is:
lone
'without company' is the definition.
(lonely)
'left a person' is the wordplay.
'left' becomes 'l' (common abbreviation).
'a person' becomes 'one' (an individual).
'l'+'one'='LONE'
(Other definitions for lone that I've seen before include "Single and isolated" , "He likes to operate by himself" , "Sole" , "Solitary or single" , "Unaccompanied" .)