Crook carried by Soviet fighter with sheep (9)
I believe the answer is:
milligram
'crook' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'carried by soviet fighter with sheep' is the wordplay.
I cannot quite understand how this works, but
'sheep' could be 'ram' (male sheep) and 'ram' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for milligram that I've seen before include "chemist's dispensing unit required?" , "not much weight" , "Small weight" , "One thousandth of a gram" , "Tiny weight" .)