A French herd to spread out (6)
I believe the answer is:
unfold
'spread out' is the definition.
(I know that spread out can be written as unfold)
'a french herd' is the wordplay.
'a french' becomes 'un' ('a' in French).
'herd' becomes 'fold' (I can't explain this - if you can you should give a lot more credence to this answer).
'un'+'fold'='UNFOLD'
'to' is the link.
Can you help me to learn more?
(Other definitions for unfold that I've seen before include "Ensue; straighten" , "Spread out or become known" , "Spread out - reveal gradually" , "Reveal - clarify" , "'O clouds, - - !' (Blake)" .)