Belleek employee about to start their first work up here (6)
I believe the answer is:
potter
'belleek employee about to start their first work up here' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'their first work up here' is the wordplay.
'their first' becomes 't' (tst letter of 'their').
'work' becomes 'op' (common abbreviation for 'opus').
'up' is a reversal indicator (in down clue: letters go upwards).
'here' becomes 'ter' (I can't explain this - if you can you should give a lot more credence to this answer).
't'+'op'='top'
'top' backwards is 'pot'.
'pot'+'ter'='POTTER'
Can you help me to learn more?
(Other definitions for potter that I've seen before include "Person who makes ceramic objects, vases etc" , "Work lightly" , "Maker of earthenware dishes" , "Wizard Harry" , "Producer of earthenware - move with little direction or energy" .)