Crying out for engine that runs without fluid, ultimately (7)
I believe the answer is:
needing
'crying out for' is the definition.
('crying out for' can mean in desperate need of)
'engine that runs without fluid ultimately' is the wordplay.
'that runs' is an anagram indicator.
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'ultimately' suggests the final letters.
The last letter of 'fluid' is 'd'.
'engine' anagrammed gives 'neeing'.
'neeing' going around 'd' is 'NEEDING'.
(Other definitions for needing that I've seen before include "Eden gin (anag.)" , "Wanting" , "Short of, lacking" , "Requiring" .)