Old coins from revolutionary republic found in improvised explosive device (7)
I believe the answer is:
denarii
'old coins' is the definition.
(I've seen this before)
'revolutionary republic found in improvised explosive device' is the wordplay.
'revolutionary' says the letters should be written backwards.
'republic' becomes 'iran' (I've seen this before).
'found in' is an insertion indicator.
'improvised explosive device' becomes 'ied'.
'iran' put within 'ied' is 'iiraned'.
'iiraned' reversed gives 'DENARII'.
'from' is the link.
(Other definitions for denarii that I've seen before include "Old coins" , "Silver coins of ancient Rome" , "Bits" , "money from abroad" , "A lot of asses" .)