Jeweller initially employed on fantastic work unit (7)
I believe the answer is:
faberge
'jeweller' is the definition.
(I've seen this before)
'initially employed on fantastic work unit' is the wordplay.
'initially' indicates taking the first letters.
'on' is a charade indicator (letters next to each other).
'fantastic' becomes 'fab' (short for fabulous).
'work unit' becomes 'erg' (erg is a kind of work unit).
The initial letter of 'employed' is 'e'.
'fab'+'erg'='faberg'
'e' after 'faberg' is 'FABERGE'.
(Other definitions for faberge that I've seen before include "Russian goldsmith known for his jewelled Easter eggs" , "fine Russian jewellery?" , "Renowned jeweller" .)