Harry a competitor in the Crucible (6)
I believe the answer is:
potter
I believe this is a double definition.
'harry' is the first definition.
(I've seen this before)
'a competitor in the crucible' is the second definition.
(as in potting balls - Crucible is a snooker venue)
(Other definitions for potter that I've seen before include "Hogwarts' Harry" , "at the wheel?" , "Person who makes ceramic objects, vases etc" , "Producer of earthenware - move with little direction or energy" , "Modeller using clay" .)