That’s a surprise, the Hoops eclipsing Hearts (3)
I believe the answer is:
oho
'that's a surprise' is the definition.
(expression of surprise)
'the hoops eclipsing hearts' is the wordplay.
I cannot quite understand how this works, but
'hearts' could be 'h' (abbreviation used in card games e.g. bridge) and 'h' is found in the answer.
'hoops' could be 'oo' (O resembles a hoop or ring) and 'oo' is found in the leftover letters.
No letters remain.
This explanation may well be incorrect...
(Other definitions for oho that I've seen before include "Expression of surprise" , "I see!" , "Triumphant cry" .)