Popular drink with one daughter, but bland (7)
I believe the answer is:
insipid
'bland' is the definition.
('insipid' can be a synonym of 'bland')
'popular drink with one daughter' is the wordplay.
'popular' becomes 'in'.
'drink' becomes 'sip' (sipping is a kind of drinking**).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'daughter' becomes 'd'.
'in'+'sip'+'i'+'d'='INSIPID'
'but' is the link.
(Other definitions for insipid that I've seen before include "without taste" , "Boring and lacking liveliness" , "Bland, flavourless" , "Lacking taste or flavour" , "Wishy-washy" .)