Brightness and passion shown by engineers (6)
I believe the answer is:
lustre
'brightness' is the definition.
(I know that lustre is a type of brightness)
'passion shown by engineers' is the wordplay.
'passion' becomes 'lust' (I've seen this before).
'shown by' is a charade indicator (letters next to each other).
'engineers' becomes 're' (abbreviation for Royal Engineers).
'lust'+'re'='LUSTRE'
'and' acts as a link.
(Other definitions for lustre that I've seen before include "Radiance; reflective surface" , "Reflected light, sheen" , "Period" , "Gloss, brightness" , "Glory; soft glow" .)