Extreme, having seen tin explode (7)
I believe the answer is:
intense
'extreme' is the definition.
(similar in meaning)
'seen tin explode' is the wordplay.
'explode' indicates an anagram.
'seen'+'tin'='seentin'
'seentin' with letters rearranged gives 'INTENSE'.
'having' is the link.
(Other definitions for intense that I've seen before include "Set nine (anag.)" , "Forceful, concentrated" , "Feverish" , "Fervent" , "Fierce - deep" .)