Demand leads for every new dog (6)
I believe the answer is:
entail
'demand' is the definition.
(I've seen this in another clue)
'leads for every new dog' is the wordplay.
'leads for' says to take the initial letters.
'dog' becomes 'tail' (synonyms).
The initial letters of 'every new' is 'en'.
'en'+'tail'='ENTAIL'
(Other definitions for entail that I've seen before include "Bring on, involve" , "Late in (anag.)" , "Involve or necessitate" , "Estate settled" , "settle estates for the long term" .)