Make a digital copy of letters related to top-secret vessel (4)
I believe the answer is:
scan
'make a digital copy of letters related' is the definition.
I can't judge whether this defines the answer.
'top-secret vessel' is the wordplay.
'top' says to take the initial letters (in a down clue, the first letter is top).
'vessel' becomes 'can' (type of container).
The first letter of 'secret' is 's'.
's'+'can'='SCAN'
'to' is the link.
Can you help me to learn more?
(Other definitions for scan that I've seen before include "Conform to a metrical pattern" , "Read superficially" , "Hercule ---, detective" , "Browse or skin over, say book" , "Inspect" .)