Arranged a gentle do to be extended (9)
I believe the answer is:
elongated
'extended' is the definition.
(I know that extended can be written as elongated)
'arranged a gentle do' is the wordplay.
'arranged' is an anagram indicator.
'a'+'gentle'+'do'='agentledo'
'agentledo' with letters rearranged gives 'ELONGATED'.
'to be' is the link.
(Other definitions for elongated that I've seen before include "Put on stretcher" , "Stretched" , "going further" , "Go al dente to be lengthened or prolonged" , "Dangle toe (anag)" .)