Old sorcerer following current line in descriptive language (7)
I believe the answer is:
imagery
'descriptive language' is the definition.
(I've seen this in another clue)
'old sorcerer following current line' is the wordplay.
'old sorcerer' becomes 'mage' (I've seen this in another clue).
'following' is a charade indicator (letters next to each other).
'current' becomes 'I' (symbol for electric current).
'line' becomes 'ry' (abbreviation for railway).
'mage' put after 'i' is 'image'.
'image'+'ry'='IMAGERY'
'in' is the link.
(Other definitions for imagery that I've seen before include "Mental visions" , "I'm gayer (anag)" , "Use of language to produce pictures in the mind" , "something easy to see?" , "The use of colourful language to make pictures in the mind" .)