A girl's secret loves simply vanish (8)
I believe the answer is:
dissolve
'vanish' is the definition.
(thesaurus)
'a girl's secret loves simply' is the wordplay.
I cannot really understand how this works, but
'girl's' could be 'dis' (Di is short for Diana) and 'dis' is located in the answer.
an anagram of 'loves' is 'solve' which is within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dissolve that I've seen before include "Pass into a solution" , "Melt in water" , "Terminate legally, partnership say" , "Incorporate a solid into a liquid" , "So devils arrange to disappear gradually" .)