Vertically challenged worker’s system of writing? (9)
I believe the answer is:
shorthand
'system of writing?' is the definition.
(writing system used when taking dictation)
'vertically challenged worker's' is the wordplay.
'vertically challenged' becomes 'short' (I've seen this in another clue).
'worker' becomes 'hand' (hand is a kind of worker).
'short'+'hand'='SHORTHAND'
(Other definitions for shorthand that I've seen before include "Pitman's invention" , "writing style" , "aid to office work?" , "Recorded words" , "Aid to taking dictation" .)