It's irritating being confined: steps inside (9)
I believe the answer is:
pestilent
'it's irritating' is the definition.
('pestilent' can be a synonym of 'irritating')
'confined steps inside' is the wordplay.
'confined' becomes 'pent' ('pent' can be similar in meaning to 'confined').
'steps' becomes 'stile' (I've seen this in other clues).
'inside' means one lot of letters goes inside another.
'pent' placed around 'stile' is 'PESTILENT'.
'being' acts as a link.
(Other definitions for pestilent that I've seen before include "Annoying" , "Peel tints (anag) - extremely tiresome" , "Lets pet in and it becomes harmful to health or life" , "Extremely harmful" , "Vexatious" .)