Egg gives engineers explosive ingredient (5)
I believe the answer is:
nitre
'explosive ingredient' is the definition.
(I've seen this before)
'egg gives engineers' is the wordplay.
I cannot quite understand how this works, but
'egg' could be 'nit' (a nit is an insect egg) and 'nit' is found within the answer.
'engineers' could be 're' (Royal Engineers) and 're' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nitre that I've seen before include "explosive ingredient" , "Otherwise saltpetre" , "explosive component" , "found in a slow match?" , "fertiliser" .)