Liquid on some lame Derby meadow (9)
I believe the answer is:
runnymede
'meadow' is the definition.
(I've seen this before)
'liquid on some lame derby' is the wordplay.
'liquid' becomes 'runny' (similar in meaning).
'on some lame derby' becomes 'mede' (I am not sure about this - if you are sure you should believe this answer much more).
'runny'+'mede'='RUNNYMEDE'
Can you help me to learn more?
(Other definitions for runnymede that I've seen before include "Magna Carta signing place" , "Here the English got charter" , "Magna Carta signing location" , "Democratic convention site" , "Place in Surrey" .)