Criticise long, and in dashing style! (7)
I believe the answer is:
panache
'dashing style' is the definition.
(I've seen this in another clue)
'criticise long' is the wordplay.
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'long' becomes 'ache' (to long for something is to ache for it).
'pan'+'ache'='PANACHE'
'and in' is the link.
(Other definitions for panache that I've seen before include "Flamboyant self-assurance" , "flourish" , "Grand manner, theatricality" , "'Dash, flair (7)'" , "A confident stylish manner" .)