Show skill as office worker, the sort to stay on the sideline? (5-4)
I believe the answer is:
touch-type
'show skill as office worker' is the definition.
(typing is a skill for an office job)
'sort to stay on the sideline?' is the wordplay.
'sort' becomes 'type' (type is a kind of sort).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'stay on the sideline?' becomes 'touch' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'type' after 'touch' is 'TOUCH-TYPE'.
'the' is the link.
(Another definition for touch-type that I've seen is " Use a keyboard without looking".)