Flinch from terribly squalid interior (5)
I believe the answer is:
quail
'flinch' is the definition.
(I know that flinch can be written as quail)
'terribly squalid interior' is the wordplay.
'terribly' indicates anagramming the letters.
'interior' indicates the central letters.
The centre of 'squalid' is 'quali'.
'quali' anagrammed gives 'QUAIL'.
'from' is the link.
(Other definitions for quail that I've seen before include "Show fear - of small game bird?" , "Flinch like gamebird" , "Shrink; a bird" , "See little bird" , "Flinch from small gamebird?" .)