Experts on English writing (5)
I believe the answer is:
prose
'writing' is the definition.
(I've seen this in another clue)
'experts on english' is the wordplay.
'experts' becomes 'pros' (professionals).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'english' becomes 'E' (abbreviation).
'pros'+'e'='PROSE'
(Other definitions for prose that I've seen before include "Not poetry" , "Non-verse" , "Ordinary writing" , "Normal written language" , "Ropes (anag.)" .)