Turk of high rank criticise like that? Ornamental blue South African flower? (10)
I believe the answer is:
agapanthus
'ornamental blue south african flower?' is the definition.
'agapanthus' can be an answer for 'flower?' (I've seen this before). I am unsure of the 'ornamental blue south african' bit.
'turk of high rank criticise like that?' is the wordplay.
'turk of high rank' becomes 'aga' (I can't justify this - if you can you should believe this answer much more).
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'like that?' becomes 'thus' (as in 'like so').
'aga'+'pan'+'thus'='AGAPANTHUS'
Can you help me to learn more?
(Other definitions for agapanthus that I've seen before include "Southern African plant of the lily family -- haunts a gap (anag)" , "Bloomer" , "flower" , "garden plant" , "Flowers" .)