Emblem may irritate endlessly (5)
I believe the answer is:
badge
'emblem' is the definition.
(badge is a kind of emblem)
'may irritate endlessly' is the wordplay.
'may' becomes 'bad' (I can't justify this - if you can you should believe this answer much more).
'irritate' becomes 'get' (I've seen this in another clue).
'endlessly' means to remove the last letter.
'get' with its last letter taken off is 'ge'.
'bad'+'ge'='BADGE'
Can you help me to learn more?
(Other definitions for badge that I've seen before include "Worn emblem" , "medal" , "Emblem signifying rank, membership etc" , "One cheating others with fictitious schemes" , "Identifying emblem" .)