Two daughters introduced to beer become confused (5)
I believe the answer is:
addle
'become confused' is the definition.
'two daughters introduced to beer' is the wordplay.
'two daughters' can mean two substitutions for 'daughters'.
'daughters' becomes 'd' (genealogical abbreviation for daughters).
'daughters' becomes 'd' (genealogical abbreviation for daughters).
'introduced to' is an insertion indicator.
'beer' becomes 'ale' (type of beer).
'd'+'d'='dd'
'dd' inserted inside 'ale' is 'ADDLE'.
(Other definitions for addle that I've seen before include "Muddle or confuse" , "Rot" , "Confuse; become rotten" , "Like a bad egg" , "Get rotten" .)