As played, yay or nay? I don't think he had flush, Ax on the other hand...
Better line would have been c/f? What if he checks behind and river is blank?
Hand converted with online PokerStrategy.com hand converter:
$0.05/$0.1 Fixed-Limit Hold'em (8 handed)
Preflop: Hero is CO with T:s, K:s.
4 folds, Hero raises, BU 3-Bets, 2 folds, Hero calls.
Flop: (7.4 SB) 4:c, K:c, 3:c (2 players)
Hero bets, BU calls.
Turn: (4.7 BB) A:d (2 players)
Hero bets, BU raises, Hero folds, BU gets uncalled bet back.
Final Pot: 5.7 BB.