Takes a duck on board (6)
I believe the answer is:
steals
'takes' is the definition.
(stealing is a kind of taking)
'a duck on board' is the wordplay.
'a duck' becomes 'teal' (teal is a type of duck).
'on' means one lot of letters goes inside another.
'board' becomes 'ss' (I can't justify this - if you can you should believe this answer much more).
'teal' placed within 'ss' is 'STEALS'.
Can you help me to learn more?
(Other definitions for steals that I've seen before include "Pilfer, filch" , "Purloins" , "Pilfers" , "Takes property without right or permission" , "Takes without owner's consent" .)