Prepared to wait as pet ain't sick? (7)
I believe the answer is:
patient
'prepared to wait' is the definition.
(I've seen this before)
'pet ain't sick?' is the wordplay.
'sick?' indicates anagramming the letters (I've seen 'sick' mean this).
'pet'+'aint'='petaint'
'petaint' is an anagram of 'PATIENT'.
'as' acts as a link.
(Other definitions for patient that I've seen before include "Person requiring medical care" , "One in hospital" , "Uncomplaining; invalid" , "One being treated" , "Unhurried" .)