Meet Rex, incredibly intense (7)
I believe the answer is:
extreme
'intense' is the definition.
(similar in meaning)
'meet rex incredibly' is the wordplay.
'incredibly' is an anagram indicator.
'meet'+'rex'='meetrex'
'meetrex' is an anagram of 'EXTREME'.
(Other definitions for extreme that I've seen before include "Far from moderate" , "Far from centre" , "Longer than usual" , "Sharp" , "Far beyond the norm" .)