Rock in some inlet crashing (9)
I believe the answer is:
limestone
'rock' is the definition.
(limestone is a kind of rock)
'some inlet crashing' is the wordplay.
'crashing' indicates an anagram.
'some'+'inlet'='someinlet'
'someinlet' anagrammed gives 'LIMESTONE'.
'in' acts as a link.
(Other definitions for limestone that I've seen before include "Tie lemons up in sedimentary rock" , "Rock of calcium carbonate" , "Clint" , "Rock, basis for caves and pavements" , "Mineral" .)