Functions of country diesel centre (4)
I believe the answer is:
uses
'functions' is the definition.
(I know this)
'country diesel centre' is the wordplay.
'country' becomes 'us' (US is an example).
'centre' indicates the central letters.
The middle letters of 'diesel' are 'es'.
'us'+'es'='USES'
'of' is the link.
(Other definitions for uses that I've seen before include "Purposes; consumes" , "deployments" , "Sues (anag.)" , "Functions, applications" , "Puts to a particular purpose" .)