Birds seen on board? (5)
I believe the answer is:
rooks
'birds seen on board?' is the definition.
'rooks' can be an answer for 'birds' (I've seen this before). I'm unsure of the 'seen on board?' bit.
This is the entire clue.
(Other definitions for rooks that I've seen before include "Large, crow-like birds" , "Overcharges" , "Fleeces; chessmen" , "Castles, also, in chess" , "Collective name for them is a parliament" .)