Map makers or graph creators, possibly (13)
I believe the answer is:
'map makers' is the definition.
('cartographer' can be a synonym of 'map maker')
'graph creators possibly' is the wordplay.
'possibly' indicates an anagram.
'graphcreators' is an anagram of 'CARTOGRAPHERS'.
'or' is the link.
(Another definition for cartographers that I've seen is " Map makers".)