Sarah's crazy to worry (6)
I believe the answer is:
harass
'worry' is the definition.
(I've seen this in another clue)
'sarah's crazy' is the wordplay.
'crazy' indicates an anagram.
'sarahs' anagrammed gives 'HARASS'.
'to' is the link.
(Other definitions for harass that I've seen before include "Annoy or badger constantly" , "Continually torment" , "Disturb < badger" , "hound" , "Annoy persistently, persecute" .)