Such a casual remark: 'Worth moving somewhere else?' (9)
I believe the answer is:
throwaway
'such a casual remark' is the definition.
(as in a throwaway remark)
'worth moving somewhere else?' is the wordplay.
'moving' indicates an anagram.
'somewhere else?' becomes 'away' (I've seen this in another clue).
'worth' anagrammed gives 'throw'.
'throw'+'away'='THROWAWAY'
(Other definitions for throwaway that I've seen before include "This remark is deliberately offhand - cast it aside" , "(Of a remark) casual, understated" , "Get rid of" , "Intended to be discarded after use" , "Made to be discarded after one use" .)