Engineer’s question heard by some (4)
I believe the answer is:
watt
'engineer's' is the definition.
(James Watt, 1736-1819)
'question heard by some' is the wordplay.
'question' becomes 'what' (what is a question word).
'heard by some' indicates a 'sounds like' (homophone) clue (homophone in some accents).
'what' sounds like 'WATT'.
(Other definitions for watt that I've seen before include "Unit of power -- Scottish engineer, d. 1819" , "Worker in steam" , "Unit of electricity" , "James - - (Scottish inventor)" , "Unit of power - Scottish inventor" .)