Need (4)
'need' is the definition.
(I know that need can be written as require)
This is all the clue.
(Other definitions for require that I've seen before include "Want, demand" , ".. must have" , "Need" , "26 [ORDER]" , "exact" .)
'need' is the definition.
(I know that want is a type of need)
This is all the clue.
(Other definitions for want that I've seen before include "Desire - deficiency" , "Wish" , "Desire to possess" , "poverty" , "Crave" .)
'need' is the definition.
(to lack something is to be in need of it)
This is all the clue.
(Other definitions for lack that I've seen before include "Deficiency (of something)" , "Dearth" , "Be wanting or without" , "Absence, deficiency" , "Deficiency or want" .)
'need' is the definition.
(synonyms)
This is the entire clue.
(Another definition for requirement that I've seen is " Necessity".)
(Other definitions for rely on that I've seen before include "Trust in with confidence" , "Put trust in" , "Trust, be confident in" .)