Leaps enthusiatically into some recess (4)
I believe the answer is:
apse
'recess' is the definition.
(apse is a kind of recess)
'leaps enthusiatically into some' is the wordplay.
'some' indicates a hidden word.
'APSE' is hidden in the letters of 'leaps enthusiatically into'.
(Other definitions for apse that I've seen before include "Large recess in church" , "Recess with domed rof in a church" , "Domed section of a church" , "part of cathedral" , "Church recess with domed or arched roof" .)