Councillor, old and restful, avoiding one game on lawn (7)
I believe the answer is:
croquet
'game on lawn' is the definition.
(I've seen this before)
'councillor old and restful avoiding one' is the wordplay.
'councillor old' becomes 'cro' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'restful' becomes 'quiet' (similar in meaning).
'avoiding' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'quiet' with 'i' taken away is 'quet'.
'cro'+'quet'='CROQUET'
Can you help me to learn more?
(Other definitions for croquet that I've seen before include "Lawn pastime" , "genteel sport" , "Mallet, hoops, game" , "Mallet sport" , "Game played with mallets (or flamingoes according to Lewis Carroll)" .)