I'm Santa, moving around, showing ability to keep going (7)
I believe the answer is:
stamina
'ability to keep going' is the definition.
(I've seen this before)
'i'm santa moving around' is the wordplay.
'moving around' is an anagram indicator.
'im'+'santa'='imsanta'
'imsanta' is an anagram of 'STAMINA'.
'showing' acts as a link.
(Other definitions for stamina that I've seen before include "energy to go on" , "grit" , "Ability to maintain effort" , "Ability for sustained effort" , "capability to keep going" .)