State “I do”, securing a husband (5)
I believe the answer is:
idaho
'state' is the definition.
(Idaho is an example)
'i do securing a husband' is the wordplay.
'securing' means one lot of letters goes inside another.
'husband' becomes 'h'.
'a'+'h'='ah'
'do' enclosing 'ah' is 'daho'.
'i'+'daho'='IDAHO'
(Other definitions for idaho that I've seen before include "US location" , "US state E. of Oregon" , "NW state of USA" , "US state bordering Canada" , "part of US near Washington" .)