Drifting round chasm (4)
I believe the answer is:
rift
'chasm' is the definition.
(I've seen this in another clue)
'drifting round' is the wordplay.
'RIFT' is hidden within the letters.
However, I am unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for rift that I've seen before include "Fissure; split" , "(Serious) break (in good relations)" , "Cleft in rock" , "A disagreement or an earth cleft" , "Schism (in the lute?)" .)