A plastic explosive produced by Moscow and Beijing (8)
I believe the answer is:
capitals
'by moscow and beijing' is the definition.
I can't judge whether this defines the answer.
'a plastic explosive' is the wordplay.
'explosive' is an anagram indicator.
'a'+'plastic'='aplastic'
'aplastic' is an anagram of 'CAPITALS'.
'produced' acts as a link.
Can you help me to learn more?
(Other definitions for capitals that I've seen before include "Major cities or large letters" , "Upper case letters" , "Great cities or large letters" , "First letters, of names say" , "First letters and first cities" .)