Work on a field of interest, like iridescent stone (7)
I believe the answer is:
opaline
'interest like iridescent stone' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?
'work on a field' is the wordplay.
'work' becomes 'op' (operation, work done in an operating theatre).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'field' becomes 'line' (both can refer to an industry or area of expertise).
'op'+'a'+'line'='OPALINE'
'of' is the link.
Can you help me to learn more?
(Other definitions for opaline that I've seen before include "Photographic plate" , "gem-like quality" , "Like some gemstones" , "whitish glass" , "Milk glass" .)