Something to heave across glacial expanse, ultimately? (6)
I believe the answer is:
sleigh
'something to heave across glacial expanse ultimately?' is the definition.
I can't tell whether this defines the answer.
'something to heave across glacial expanse ultimately?' is the wordplay.
'something to heave' becomes 'sigh' (you might heave a sigh of relief).
'across' indicates putting letters inside.
'ultimately?' suggests the final letters (I've seen 'ultimately' mean this).
The last letters of 'glacial expanse' are 'le'.
'sigh' placed around 'le' is 'SLEIGH'.
(Other definitions for sleigh that I've seen before include "transport (with bells on!)" , "13 ac's transport" , "Toboggan" , "Horse-drawn sledge" , "Transport in winter" .)