Nobleman dies - guillotined on time. Most punctual! (8)
I believe the answer is:
earliest
'most punctual' is the definition.
Both the answer and definition are superlative adjectives. Maybe you can see an association between them that I can't see?
'nobleman dies guillotined on time' is the wordplay.
'nobleman' becomes 'earl' (earl is a kind of nobleman).
'guillotined' means to remove the first letter.
'on' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'dies' with its initial letter removed is 'ies'.
'earl'+'ies'+'t'='EARLIEST'
Can you help me to learn more?
(Other definitions for earliest that I've seen before include "Nearest the start of a time period" , "The first to arrive - to get the worm?" , "Next available" , "Soonest" , "Very first in a sterile manner" .)