Fantastic Four infiltrating premises in disguise (10)
I believe the answer is:
impressive
'fantastic' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'four infiltrating premises in disguise' is the wordplay.
'four' becomes 'IV' (Roman numerals).
'infiltrating' indicates putting letters inside.
'in disguise' indicates anagramming the letters.
'premises' with letters rearranged gives 'impresse'.
'iv' going into 'impresse' is 'IMPRESSIVE'.
Can you help me to learn more?
(Another definition for impressive that I've seen is " Moving".)