Cereal required by every engineer (3)
I believe the answer is:
rye
'cereal' is the definition.
(I know that rye is a type of cereal)
'required by every engineer' is the wordplay.
'required by' indicates a hidden word (the answer is required to spell part of the clue).
'RYE' can be found hidden inside 'every engineer'.
(Other definitions for rye that I've seen before include "Hardy cereal crop" , "Whisky; Sussex town" , "J D Salinger novel 'The Catcher in the ...'" , "Burns's body came through" , "American whisky" .)