Loads of room in a short top (5)
I believe the answer is:
acres
'loads of room' is the definition.
(an acre is a measurement of space or area)
'a short top' is the wordplay.
'short' means to remove the last letter.
'top' becomes 'crest' (crest can mean the top of a hill).
'crest' with its final letter removed is 'cres'.
'a'+'cres'='ACRES'
'in' is the link.
(Other definitions for acres that I've seen before include "One of them has 4840 square yards" , "Imperial units or measures of land" , "The Phoenix Park has 40 of them (5)" , "Scare (anag)" , "Land area measures" .)