Precise former spouse has to do something (5)
I believe the answer is:
exact
'precise' is the definition.
(I know that precise can be written as exact)
'former spouse has to do something' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'has' says to put letters next to each other.
'to do something' becomes 'act' (to act is to do something).
'ex'+'act'='EXACT'
(Other definitions for exact that I've seen before include "Faithful" , "Specific" , "As a right, demand" , "Precise - demand" , "Particular" .)