Shortest time confronting most irritating (9)
I believe the answer is:
titchiest
'shortest' is the definition.
(titchy means small or short)
'time confronting most irritating' is the wordplay.
'time' becomes 't' (abbreviation).
'confronting' means one lot of letters go next to another.
'most irritating' becomes 'itchiest' (I've seen this before).
't'+'itchiest'='TITCHIEST'
(Other definitions for titchiest that I've seen before include "smaller than all the others" , "Smallest" .)