A counterfeit piastre won't be heard when dropped (8)
I believe the answer is:
aspirate
'won't be heard when dropped' is the definition.
I can't judge whether this defines the answer.
'a counterfeit piastre' is the wordplay.
'counterfeit' is an anagram indicator.
'piastre' is an anagram of 'spirate'.
'a'+'spirate'='ASPIRATE'
Can you help me to learn more?
(Other definitions for aspirate that I've seen before include "Breathed consonant" , "The sound of h from parasite" , "Breathe in; sound of h" , "Sound one's Hs" , "how he lived his life" .)