Miles above the ground collecting temperature data (8)
I believe the answer is:
material
'data' is the definition.
(thesaurus)
'miles above the ground collecting temperature' is the wordplay.
'miles' becomes 'm' (abbreviation).
'above the ground' becomes 'aerial' (ie in the sky).
'collecting' means one lot of letters goes inside another.
'temperature' becomes 't' (abbreviation).
'aerial' enclosing 't' is 'aterial'.
'm'+'aterial'='MATERIAL'
(Other definitions for material that I've seen before include "grave" , "Relevant sort of cloth?" , "Cloth, fabric" , "Fabric or other substance" , "Directly relevant to a matter, in a law case perhaps" .)