Lowers cold beer, with teetotaller entering (6)
I believe the answer is:
cattle
'lowers' is the definition.
(I've seen this before)
'cold beer with teetotaller entering' is the wordplay.
'cold' becomes 'C' (abbreviation, eg on taps).
'beer' becomes 'ale' (type of beer).
'with' means one lot of letters go next to another.
'teetotaller' becomes 'tt' (abbreviation).
'entering' is an insertion indicator.
'c'+'ale'='cale'
'cale' placed around 'tt' is 'CATTLE'.
(Other definitions for cattle that I've seen before include "Jersey and Guernsey?" , "Farm animals" , "New York district" , "Bovine creatures" , "Livestock, kine" .)