Publication by American sorcerer of old (5)
I believe the answer is:
magus
'sorcerer of old' is the definition.
'magus' can be an answer for 'sorcerer' (magus is a kind of sorcerer). I'm unsure of the 'of old' bit.
'publication by american' is the wordplay.
'publication' becomes 'mag' (abbreviation for magazine).
'by' means one lot of letters go next to another.
'american' becomes 'us' (abbreviation for United States).
'mag'+'us'='MAGUS'
Can you help me to learn more?
(Other definitions for magus that I've seen before include "Gift-bearing Wise Man" , "Guru" , "Sorcerer" , "eg Melchior" , "Wizard" .)