I ignore VAT being fiddled in rally (10)
I believe the answer is:
invigorate
'rally' is the definition.
(thesaurus)
'i ignore vat being fiddled' is the wordplay.
'being fiddled' indicates anagramming the letters.
'ignore'+'vat'='ignorevat'
'ignorevat' is an anagram of 'nvigorate'.
'i'+'nvigorate'='INVIGORATE'
'in' is the link.
(Other definitions for invigorate that I've seen before include "Give strength to" , "Liven up" , "Give energy to" , "Strengthen" , "Perk up" .)