Calmly suggest husband must break secret (8)
I believe the answer is:
smoothly
'calmly' is the definition.
(thesaurus)
'suggest husband must break secret' is the wordplay.
'suggest' becomes 'moot' (I can't explain this - if you can you should believe this answer much more).
'husband' becomes 'h'.
'must break' indicates putting letters inside (inserted letters break into the word).
'secret' becomes 'sly' (I've seen this in other clues).
'moot'+'h'='mooth'
'mooth' inserted into 'sly' is 'SMOOTHLY'.
Can you help me to learn more?
(Other definitions for smoothly that I've seen before include "Evenly, regularly" , "Evenly, with no problems or difficulties" , "Evenly or with no difficulty" .)