Everlasting pearl - nine forms (9)
I believe the answer is:
perennial
'everlasting' is the definition.
(I've seen this in another clue)
'pearl nine forms' is the wordplay.
'forms' indicates an anagram.
'pearl'+'nine'='pearlnine'
'pearlnine' with letters rearranged gives 'PERENNIAL'.
(Other definitions for perennial that I've seen before include "Constantly recurring like some plants" , "Constantly recurring or lasting, like plant" , "Plant that lives for a number of years" , "Constant" , "Everlasting" .)