Press finally employ literary device (5)
I believe the answer is:
irony
'literary device' is the definition.
(I've seen this in another clue)
'press finally employ' is the wordplay.
'press' becomes 'iron' (ironing is a kind of pressing).
'finally' says to take the final letters.
The final letter of 'employ' is 'y'.
'iron'+'y'='IRONY'
(Other definitions for irony that I've seen before include "Kind of sarcasm, sounds metallic" , "form of sarcasm" , "the reverse of what you'd expect" , "It could be hard" , "Socratic method of discussion" .)