Concerning identical item used for second head-to-head (7)
I believe the answer is:
rematch
'concerning identical item' is the definition.
The definition suggests a singular noun which matches the answer.
'second head-to-head' is the wordplay.
'second' becomes 're' (prefix meaning second in eg review, re-education).
'head-to-head' becomes 'match' (I can't justify this - if you can you should give a lot more credence to this answer).
're'+'match'='REMATCH'
'used for' acts as a link.
Can you help me to learn more?
(Other definitions for rematch that I've seen before include "Another game" , "Later encounter" , "Teams' second game" , "Return fixture" , "Further engagement of the same contestants" .)