China facing retreat over data (8)
I believe the answer is:
material
'data' is the definition.
(thesaurus)
'china facing retreat over' is the wordplay.
'china' becomes 'mate' ('China plate' is rhyming slang for 'mate').
'facing' says to put letters next to each other.
'retreat' becomes 'lair' (I've seen this before).
'over' says the letters should be written in reverse.
'lair' written backwards gives 'rial'.
'mate'+'rial'='MATERIAL'
(Other definitions for material that I've seen before include "of serious importance" , "grave" , "Relevant sort of cloth?" , "Constituents" , "Relevant - fabric" .)