Move fast to get a small something to chew! (4)
I believe the answer is:
scud
'move fast' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'get a small something to chew' is the wordplay.
'get' means one lot of letters go next to another.
'a small' becomes 's' (abbreviation - e.g. clothes size).
'something to chew' becomes 'cud' (I can't justify this - if you can you should believe this answer much more).
's' next to 'cud' is 'SCUD'.
'to' is the link.
Can you help me to learn more?
(Other definitions for scud that I've seen before include "Gust of wind" , "Condition of streaker at Murrayfield" , "(Of a cloud) move very quickly" , "Move quickly (as if running before a gale)" , "Ballistic missile; sweep along" .)