Write – "John Hancock” (4)
I believe the answer is:
'write' is the definition.
(I know that sign is a more specific form of the action the write)
'john hancock' is the wordplay.
I cannot quite see how this works, but
'john hancock' could be 'sig' (I've seen this in another clue) and 'sig' is found within the answer.
A single letter 'n' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sign that I've seen before include "Public notice; Leo, say" , "information board?" , "house" , "Public notice; portent" , "Ram" .)