Legally retaliate to little Suzanne under the table (10)
I believe the answer is:
countersue
'legally' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'retaliate to little suzanne under the table' is the wordplay.
'retaliate' becomes 'counter' (I've seen this before).
'to little' suggests taking the first letters.
'under the table' becomes 'ue' (I can't justify this - if you can you should give a lot more credence to this answer).
The initial letter of 'suzanne' is 's'.
'counter'+'s'+'ue'='COUNTERSUE'
Can you help me to learn more?
(Another definition for countersue that I've seen is " return to action?".)