German law-maker heads to open Hamburg museum (3)
I believe the answer is:
ohm
'german law-maker' is the definition.
I can't judge whether this defines the answer.
'heads to open hamburg museum' is the wordplay.
'heads to' says to take the initial letters (I've seen 'heading to' mean this (the head of the word)).
The initial letters of 'open hamburg museum' is 'OHM'.
Can you help me to learn more?
(Other definitions for ohm that I've seen before include "measure of resistance" , "lawmaker" , "SI unit of electrical resistance" , "physical unit" , "Unit of electrical resistance (3)" .)