Getting less than a firkin can vex one (3)
I believe the answer is:
irk
'vex one' is the definition.
'irk' can be an answer for 'vex' (I've seen this in another clue). I'm not certain of the 'one' bit.
'getting less than a firkin' is the wordplay.
'IRK' is hidden in amongst the letters.
However, I am unsure how the hidden word is indicated.
'can' is the link.
Can you help me to learn more?
(Other definitions for irk that I've seen before include "Irritate, vex" , "Irritate, annoy" , "upset" , "English river" , "Severely annoy" .)