Bear that wrestled with monarch is very impressive (12)
I believe the answer is:
breathtaking
'very impressive' is the definition.
'breathtaking' can be an answer for 'impressive' (thesaurus). I'm not certain of the 'very' bit.
'bear that wrestled with monarch' is the wordplay.
'wrestled' is an anagram indicator (I've seen 'wrestle' mean this (I've seen this in other clues)).
'with' means one lot of letters go next to another.
'monarch' becomes 'king' (king is a kind of monarch).
'bear'+'that'='bearthat'
'bearthat' with letters rearranged gives 'breathta'.
'breathta'+'king'='BREATHTAKING'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for breathtaking that I've seen before include "if one is not one is dead?" , "Causing astonishment" , "way of getting air into the lungs" , "Awe-inspiring" , "Moving" .)