Press release about bishop — it's explosive (4,4)
I believe the answer is:
time bomb
'explosive' is the definition.
'press release about bishop' is the wordplay.
'press' becomes 'mob' (I've seen this before).
'release' becomes 'emit' (emitting is a kind of releasing**).
'about' says the letters should be written backwards.
'bishop' becomes 'b' (abbreviation used in chess).
'mob'+'emit'='mobemit'
'mobemit' reversed gives 'timebom'.
'timebom'+'b'='TIME-BOMB'
'it's' is the link.
(Other definitions for time bomb that I've seen before include "one could go off after a while" , "weapon" , "Scheduled report" , "Exploding ticker?" , "Preset explosive device" .)