O'Sullivan's third trick shot enthrals the UK, for one (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Third letter of [os] U [llivan], contained in (. . . enthrals) CON (trick = deception) + TRY (shot = an attempt, as in “give it a shot”). The surface appears to refer to the snooker player Ronnie O’Sullivan.