Calls one's better half 'Ms' (5)
I believe the answer is:
terms
'calls one's' is the definition.
'terms' can be an answer for 'calls' (terming is a kind of calling). I'm unsure of the 'one's' bit.
'better half ms' is the wordplay.
'better half' becomes 'ter'.
'ter'+'ms'='TERMS'
Can you help me to learn more?
(Other definitions for terms that I've seen before include "words" , "Stipulated requirements" , "Stipulations, often joined to conditions" , "Conditions for agreement" , "Phrases" .)