Sounding drunk, Ms Merkel’s not quite square? (11)
I believe the answer is:
rectangular
'square?' is the definition.
('rectangular' can be similar in meaning to 'square')
'sounding drunk ms' is the wordplay.
'sounding' indicates a 'sounds like' (homophone) clue.
'drunk' becomes 'wrecked'.
'ms' becomes 'angular' (I can't justify this - if you can you should believe this answer much more).
'wrecked' sounds like 'rect'.
'rect'+'angular'='RECTANGULAR'
'merkel's not quite' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rectangular that I've seen before include "Oblong" , "A four-shaped, perhaps" , "Of a right-angled parallelogram" , "to be at ninety degrees" , "flag, for example" .)