Tongue of land surrounding a lake that's overflowed (5)
I believe the answer is:
spilt
'overflowed' is the definition.
(I've seen this before)
'tongue of land surrounding a lake' is the wordplay.
'tongue of land' becomes 'spit' (I can't justify this - if you can you should give a lot more credence to this answer).
'surrounding' indicates putting letters inside.
'a lake' becomes 'l'.
'spit' placed around 'l' is 'SPILT'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for spilt that I've seen before include "Poured forth" , "(Liquid) slopped" , "Overflowed" , "(Of liquid) dropped" , "Slopped over the edge" .)