Sardonic and cautious, dismissing article (3)
I believe the answer is:
wry
'sardonic' is the definition.
(thesaurus)
'and cautious dismissing article' is the wordplay.
'and' becomes 'n' (common abbreviation for 'and').
'cautious' becomes 'wary' ('wary' can be similar in meaning to 'cautious').
'dismissing' is a deletion indicator.
'article' becomes 'an' (indefinite article).
'n'+'wary'='nwary'
'nwary' with 'an' removed is 'WRY'.
(Other definitions for wry that I've seen before include "Of humour, dry and mocking" , "Crooked - droll" , "Perverse" , "Mockingly humorous" , "Ironically humorous" .)