Without room to wriggle (4)
I believe the answer is:
worm
'wriggle' is the definition.
(worming is a kind of wriggling)
'without room' is the wordplay.
'without' becomes 'wo' (abbreviation of 'without', normally with a slash).
'room' becomes 'rm' (I've seen this in other clues).
'wo'+'rm'='WORM'
'to' is the link.
(Other definitions for worm that I've seen before include "Wretched person" , "Wriggle" , "one leaving cast" , "Creeping invertebrate" , "Cylindrical gear; burrowing invertebrate" .)