Rich husband setting limits to one’s fidelity (5)
I believe the answer is:
faith
'fidelity' is the definition.
(thesaurus)
'rich husband setting limits to one's' is the wordplay.
'rich' becomes 'fat' (synonyms).
'husband' becomes 'h'.
'setting limits to' means one lot of letters goes inside another (outside letters limit or restrain the rest).
'one' becomes 'I' (Roman numeral).
'fat'+'h'='fath'
'fath' placed around 'i' is 'FAITH'.
(Other definitions for faith that I've seen before include "Unshakeable belief" , "A woman" , "'..... will move mountains'" , "Confidence" , "Staunch trust" .)