It’s annoying, and I ultimately bluster and yell when holding it (8)
I believe the answer is:
irritant
'it's annoying' is the definition.
(I've seen this before)
'i ultimately bluster and yell when holding it' is the wordplay.
'ultimately' says to take the final letters.
'and' says to put letters next to each other.
'yell' becomes 'rant' (rant can mean to yell or shout).
'when holding' means one lot of letters goes inside another.
The last letter of 'bluster' is 'r'.
'rant' placed around 'it' is 'ritant'.
'i'+'r'+'ritant'='IRRITANT'
'and' acts as a link.
(Other definitions for irritant that I've seen before include "Something that causes annoyance and bad temper" , "Something that chafes or annoys" , "Source of continual annoyance" , "Annoying thing" , "Cause of itch" .)