In case of collapse, call shrink (6)
I believe the answer is:
cringe
'shrink' is the definition.
(I know that shrink can be written as cringe)
'in case of collapse call' is the wordplay.
'in' indicates putting letters inside.
'case of' suggests removing the centre (like emptying a case).
'call' becomes 'ring' (telephone call).
'collapse' with its middle taken out is 'ce'.
'ce' placed around 'ring' is 'CRINGE'.
(Other definitions for cringe that I've seen before include "Shrink in fear, embarrassment, or servility" , "Squirm" , "Cower, shrink in fear" , "Sneak" , "Shrink away in fear" .)