Swimmers emptied two glasses (4)
I believe the answer is:
togs
'swimmers emptied two glasses' is the definition.
I can't tell whether this defines the answer.
'emptied two glasses' is the wordplay.
'emptied' means to remove the middle letters.
'glasses' becomes 'gs' (I can't justify this - if you can you should believe this answer much more).
'two' with its middle removed is 'to'.
'to'+'gs'='TOGS'
Can you help me to learn more?
(Other definitions for togs that I've seen before include "Gear" , "garment" , "costumes [STRINE]" , "Clothes (sl.)" , "Swimsuit" .)