Start to pick on barmaids? Perhaps they can (10)

'they can' is the definition.
Although both the answer and 'can' are nouns, they are not in the same form of the noun.

'start to pick on barmaids?' is the wordplay.
'start to' indicates taking the first letters.
'on' becomes 're' ('on' can be mean 'with reference to').
'barmaids?' becomes 'servers' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letter of 'pick' is 'p'.
'p'+'re'+'servers'='PRESERVERS'

'perhaps' is the link.

Can you help me to learn more?