Old skill making a comeback for spear-carrier (5)
I believe the answer is:
extra
'spear-carrier' is the definition.
(I've seen this before)
'old skill making a comeback' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'skill' becomes 'art' (both can mean a talent).
'making a comeback' shows that the letters should be reversed in order.
'art' reversed gives 'tra'.
'ex'+'tra'='EXTRA'
'for' acts as a link.
(Other definitions for extra that I've seen before include "Surcharge" , "Supplemental" , "Unnecessary" , "Left over" , "no ball perhaps" .)