Improperly confined, plainly seen around, too assured (13)
I believe the answer is:
overconfident
'too assured' is the definition.
'overconfident' can be an answer for 'assured' (thesaurus). I'm unsure of the 'too' bit.
'improperly confined plainly seen around' is the wordplay.
'improperly' indicates an anagram (I've seen this in other clues).
'plainly seen' becomes 'overt' (I can't explain this - if you can you should give a lot more credence to this answer).
'around' indicates putting letters inside.
'confined' is an anagram of 'confiden'.
'confiden' going within 'overt' is 'OVERCONFIDENT'.
Can you help me to learn more?
(Other definitions for overconfident that I've seen before include "Cock-sure" , "Too bold or certain" , "Too certain of oneself" , "Too bullish" , "Too sure of oneself" .)