Lady Bert is pouring a drink for (7)
I believe the answer is:
sherbet
'drink for' is the definition.
'sherbet' can be an answer for 'drink' (I've seen this before). I'm not sure about the 'for' bit.
'lady bert is pouring a' is the wordplay.
I cannot really understand how this works, but
'lady' could be 'sher' and 'sher' is located in the answer.
'is' could be 'be' and 'be' is found within the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sherbet that I've seen before include "Fizzy stuff" , "Sweet fizzy, fruity, drink" , "A fizzy drink, a fruit drink" , "Australian beer" , "iced food" .)