Architectural style about right? That's sarcastic! (6)
I believe the answer is:
ironic
'sarcastic' is the definition.
('ironic' can be similar in meaning to 'sarcastic')
'architectural style about right?' is the wordplay.
'architectural style' becomes 'ionic' (I've seen this before).
'about' indicates putting letters inside.
'right?' becomes 'r' (common abbreviation).
'ionic' going around 'r' is 'IRONIC'.
'that's' acts as a link.
(Other definitions for ironic that I've seen before include "Meaning the contrary of what is expressed" , "Characterised by mildly sardonic wit" , "Sarcastic, expressing meaning by invoking opposite" , "Wryly amusing" , "Double-edged" .)