Fluid end with legato stretched out (9)
I believe the answer is:
elongated
'stretched out' is the definition.
(I've seen this before)
'fluid end with legato' is the wordplay.
'fluid' is an anagram indicator.
'with' says to put letters next to each other.
'end' after 'legato' is 'legatoend'.
'legatoend' anagrammed gives 'ELONGATED'.
(Other definitions for elongated that I've seen before include "Put on stretcher" , "Stretched" , "Dangle toe (anag)" , "Go al dente to be lengthened or prolonged" , "going further" .)