An Irishman's butter? (4)
I believe the answer is:
pats
'an irishman's butter?' is the definition.
Although both the answer and 'butter?' are verbs, they are not in the same form of the verb.
'irishman's butter?' is the wordplay.
'irishman' becomes 'Pat' (Patrick is a common Irish name).
'butter?' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pat'+'s'='PATS'
Can you help me to learn more?
(Another definition for pats that I've seen is " Light touches or strokes".)