4th hand at the table. Donked for over pot. What type of hand is he protecting here? What's hero's action?

PokerStars No-Limit Hold'em, $0.25 BB (5 handed) from (Format: Bet The Pot)

SB ($10)
BB ($25.35)
UTG ($21.35)
Hero ($24.90)
Button ($4.90)

Preflop: Hero is MP with , .
UTG calls $0.25, Hero raises to $1.25, Button calls $1.25, 2 folds, UTG calls $1.

Flop: ($4.10) , , (3 players)
UTG bets $4.75

Call/re-evaluate.