Punctuation mark used by male in company with graduate (5)
I believe the answer is:
comma
'punctuation mark' is the definition.
(I know that comma is a type of punctuation mark)
'male in company with graduate' is the wordplay.
'male' becomes 'm' (common abbreviation).
'in' means one lot of letters goes inside another.
'company' becomes 'co' (abbreviation).
'with' says to put letters next to each other.
'graduate' becomes 'MA' (abbreviation for Master of Arts).
'co'+'ma'='coma'
'm' placed within 'coma' is 'COMMA'.
'used by' is the link.
(Other definitions for comma that I've seen before include "part of list, invariably" , "Kind of butterfly" , "Common punctuation park" , "Mark for smallest division of a sentence" , "List-item separator" .)