Gets close in linear size (5)
I believe the answer is:
nears
'gets close' is the definition.
(I've seen this in another clue)
'in linear size' is the wordplay.
'in' indicates a hidden word.
'NEARS' is hidden within 'linear size'.
(Other definitions for nears that I've seen before include "Approaches - snare (anag)" , "Draws close" , "Gets closer" , "Comes closer" , "Bears down" .)