Domestic pet about to return, so put food out? (5)
I believe the answer is:
cater
'put food out?' is the definition.
(to cater is to provide food)
'domestic pet about to return' is the wordplay.
'domestic pet' becomes 'cat'.
'about' becomes 're' ('re' means regarding or about).
'to return' says the letters should be written in reverse.
're' in reverse letter order is 'er'.
'cat'+'er'='CATER'
'so' acts as a link.
(Other definitions for cater that I've seen before include "Supply food and drink" , "Provide what is required" , "Provide what is needed or wanted" , "Trace (anag.)" , "Make provision for" .)