Elaborate penalty given to engineers (6)
I believe the answer is:
refine
'elaborate' is the definition.
('refine' can be a synonym of 'elaborate')
'penalty given to engineers' is the wordplay.
'penalty' becomes 'fine' (fine is a kind of penalty).
'given to' means one lot of letters go next to another.
'engineers' becomes 're' (Royal Engineers).
'fine' after 're' is 'REFINE'.
(Other definitions for refine that I've seen before include "Get rid of impurities" , "Hone" , "Make purer" , "Filter or process as with oil" , "Cleanse from impurities" .)