Lump of rock caught cleaner (4)
I believe the answer is:
crag
'lump of rock' is the definition.
'crag' can be an answer for 'rock' (I've seen this before). I'm not sure about the 'lump of' bit.
'caught cleaner' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'cleaner' becomes 'rag' (I can't justify this - if you can you should give a lot more credence to this answer).
'c'+'rag'='CRAG'
Can you help me to learn more?
(Other definitions for crag that I've seen before include "Steep, rugged peak" , "Avant-garde" , "Steep or rugged cliff face" , "Steep rugged rock or cliff" , "Rocky hilltop" .)