Lots of you once going to beaches (9)
I believe the answer is:
thousands
'lots' is the definition.
The answer and definition can be both quantities as well as being plural nouns.
Maybe you can see an association between them that I can't see?
'you once going to beaches' is the wordplay.
'you once' becomes 'thou' (historical second person pronoun).
'going to' means one lot of letters go next to another.
'beaches' becomes 'sands' (I've seen this before).
'thou'+'sands'='THOUSANDS'
'of' is the link.
Can you help me to learn more?
(Other definitions for thousands that I've seen before include "a lot" , "1000s" , "Crowds" , "Large numbers" , "Dan shouts out at many hundreds" .)