Has to renew promises (5)
I believe the answer is:
oaths
'promises' is the definition.
(I know this)
'has to renew' is the wordplay.
'renew' indicates an anagram (I've seen 'renewing' mean this).
'has'+'to'='hasto'
'hasto' anagrammed gives 'OATHS'.
(Other definitions for oaths that I've seen before include "Swearwords" , "Curses - words of honour?" , "Solemn vows" , "truths may be established by them" , "Cursing" .)