Snatches short sleep on board (5)
I believe the answer is:
snaps
'snatches' is the definition.
('snap' can be a synonym of 'snatch')
'sleep on board' is the wordplay.
'sleep' becomes 'nap' (a nap is a short sleep).
'on' means one lot of letters goes inside another.
'board' becomes 'ss' (I can't explain this - if you can you should give a lot more credence to this answer).
'nap' put within 'ss' is 'SNAPS'.
'short' acts as a link.
(Other definitions for snaps that I've seen before include "Breaks under tension" , "Photos" , "Breaks suddenly" , "Informal photographs" , "Breaks in two" .)