Demand fellows, leaving out first of them, to follow (6)
I believe the answer is:
entail
'demand' is the definition.
(thesaurus)
'to follow' is the wordplay.
'to' becomes 'en' (I can't explain this - if you can you should believe this answer much more).
'follow' becomes 'tail' (both can mean to chase or pursue).
'en'+'tail'='ENTAIL'
'fellows leaving out first of them' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for entail that I've seen before include "Inalienable estate" , "Have as a logical consequence" , "Need" , "Bring on an inevitable consequence" , "Involve or make necessary" .)