Means the half of bitter sent in is weak and insipid (6)
I believe the answer is:
watery
'insipid' is the definition.
(I've seen this before)
'means the half of bitter sent in is weak' is the wordplay.
I cannot quite understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'weak' could be 'w' (physics symbol as in W-boson) and 'w' is found in the answer.
The remaining letters 'aery' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for watery that I've seen before include "(Of food) thin, tasteless" , "Aqueous" , "Overly diluted, thin" , "Weak, too diluted" , "Dilute; weak, pale" .)