Fleeting romp turned into weeping (9)
I believe the answer is:
temporary
'fleeting' is the definition.
(thesaurus)
'romp turned into weeping' is the wordplay.
'turned' is an anagram indicator.
'into' means one lot of letters goes inside another.
'weeping' becomes 'teary' (I've seen this before).
'romp' anagrammed gives 'mpor'.
'mpor' inserted inside 'teary' is 'TEMPORARY'.
(Other definitions for temporary that I've seen before include "Not for long" , "Lasting for a limited period" , "Impermanent" , "not for good" , "Lasting a short time" .)