Minor employee from firm heading for glory (3)
I believe the answer is:
cog
'minor employee' is the definition.
(I've seen this before)
'firm heading for glory' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'heading for' says to take the initial letters.
The first letter of 'glory' is 'g'.
'co'+'g'='COG'
'from' is the link.
(Other definitions for cog that I've seen before include "bar" , "Little gearwheel" , "Junior official" , "Gear-tooth" , "Wheel with projections" .)