Press piece regularly seen as sarcastic (6)
I believe the answer is:
ironic
'sarcastic' is the definition.
('ironic' can be similar in meaning to 'sarcastic')
'press piece regularly seen' is the wordplay.
'press' becomes 'iron' (ironing is a kind of pressing).
'regularly seen' means one should take alternating letters.
The alternating letters of 'piece' are 'ic'.
'iron'+'ic'='IRONIC'
'as' acts as a link.
(Other definitions for ironic that I've seen before include "Wryly satirical" , "Perversely amusing" , "'Wry, incongruous (6)'" , "(Of a happening) having significance not perceived at the time" , "not as you'd expect" .)