Open over committee (5-5)
I believe the answer is:
above-board
'open' is the definition.
(I've seen this before)
'over committee' is the wordplay.
'over' becomes 'above' (I've seen this in another clue).
'committee' becomes 'board' (board is a kind of committee).
'above'+'board'='ABOVE-BOARD'
(Other definitions for above-board that I've seen before include "Honest" , "Straight" .)