Thinking of confusing VAT incomplete (13)
I believe the answer is:
contemplative
'thinking' is the definition.
(thesaurus)
'confusing vat incomplete' is the wordplay.
'confusing' indicates an anagram.
'vat'+'incomplete'='vatincomplete'
'vatincomplete' anagrammed gives 'CONTEMPLATIVE'.
'of' is the link.
(Other definitions for contemplative that I've seen before include "Thoughtful" , "Employing meditation" , "lost in thought" .)