RAF woman designed armed sea-going vessel (3-2-3)
I believe the answer is:
man-of-war
'armed sea-going vessel' is the definition.
'man-of-war' can be an answer for 'vessel' (man-of-war is a kind of vessel). I am not certain of the 'armed sea-going' bit.
'raf woman designed' is the wordplay.
'designed' indicates anagramming the letters (designed with the letters).
'raf'+'woman'='rafwoman'
'rafwoman' anagrammed gives 'MAN-OF-WAR'.
Can you help me to learn more?
(Other definitions for man-of-war that I've seen before include "Portuguese --, jellyfish" , "Armed sailing ship" , "Old naval ship" , "A battleship - for a fighter?" , "Fighting ship" .)