Initial contract left with 2.54cm to confirm (6)
I believe the answer is:
clinch
'to confirm' is the definition.
(thesaurus)
'initial contract left with 2' is the wordplay.
'initial' suggests taking the first letters.
'with n' becomes 'inch' (I can't justify this - if you can you should give a lot more credence to this answer).
The first letters of 'contract left' is 'cl'.
'cl'+'inch'='CLINCH'
'54cm' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for clinch that I've seen before include "Clutch" , "Fasten securely or settle conclusively" , "Confirm - embrace" , "Drive home (an argument)" , "Matthew ---; --- Schoenberg" .)