A tax collector ultimately beyond a two-dimensional icon (6)
I believe the answer is:
avatar
'two-dimensional icon' is the definition.
'avatar' can be an answer for 'icon' (an online icon or image). I'm unsure of the 'two-dimensional' bit.
'a tax collector ultimately beyond a' is the wordplay.
'tax' becomes 'vat' (UK Value Added Tax).
'ultimately' suggests the final letters.
'beyond' is a charade indicator (letters next to each other).
The last letter of 'collector' is 'r'.
'r' put after 'a' is 'ar'.
'a'+'vat'+'ar'='AVATAR'
Can you help me to learn more?
(Other definitions for avatar that I've seen before include "Descent to earth of deity in human or animal form" , "Person who embodies a particular ideal" , "Graphic" , "In Hinduism, the descent to earth of a deity" , "Manifestation of person or idea" .)