Frigg finally seen in this swirling vision (5)
I believe the answer is:
sight
'vision' is the definition.
(synonyms)
'frigg finally seen in this swirling' is the wordplay.
'finally' says to take the final letters.
'seen in' is an insertion indicator.
'swirling' is an anagram indicator.
The final letter of 'frigg' is 'g'.
'this' with letters rearranged gives 'siht'.
'g' going within 'siht' is 'SIGHT'.
(Other definitions for sight that I've seen before include "The ability to see - spectacle" , "Sense" , "Power of vision" , "Seeing" , "A great many" .)