Elevation, with second in line moving to the top, gives breathing space (8)
I believe the answer is:
latitude
'space' is the definition.
(thesaurus)
'elevation with second in line moving to the top gives breathing' is the wordplay.
I cannot quite understand how this works, but
'second' could be 'd' and 'd' is found in the answer.
'line' could be 'l' (used when specifying particular lines from a poem) and 'l' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'top' could be 'ai' (I've seen this in other clues) and 'ai' is found within the remaining letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for latitude that I've seen before include "Liberality" , "Unrestricted" , "lines on a map" , "global cover to some degree?" , "Scope (with parallel circles?)" .)