Deficiency in gear host fixed (8)
I believe the answer is:
shortage
'deficiency' is the definition.
(I know that shortage is a type of deficiency)
'gear host fixed' is the wordplay.
'fixed' indicates anagramming the letters.
'gear'+'host'='gearhost'
'gearhost' with letters rearranged gives 'SHORTAGE'.
'in' acts as a link.
(Other definitions for shortage that I've seen before include "Want" , "Dearth, lack" , "Lack, deficiency" , "Horse tag (anag.)" , "Her goats (anag)" .)