Trusted engineers weren't honest (6)
I believe the answer is:
relied
'werent honest' is the definition.
I can't tell whether this defines the answer.
'trusted engineers' is the wordplay.
I cannot really see how this works, but
'engineers' could be 're' (abbreviation for Royal Engineers) and 're' is found within the answer.
The remaining letters 'lied' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for relied that I've seen before include "Banked" , "Depended or counted on" , "Assembled as before" , "Had confidence" , "Was dependent (on)" .)