Bed starts to creak — replace its base (4)
I believe the answer is:
Here is my best explanation:
'bed' is the definition.
'starts to creak replace its base' is the wordplay.
'starts to' says to take the initial letters.
The initial letters of 'creak replace its base' is 'CRIB'.
(Other definitions for crib that I've seen before include "Infant's bed", "Steal - key - child's bed", "A baby's cot in America", "model much in evidence at Christmas", "Pirate", "Poor translation", "Nativity centrepiece", "Child's bed - copy", "Child's cot" and "Container for animal fodder".)