Give to the new-formed party therein (5)
I believe the answer is:
endow
'give' is the definition.
(endow can mean to give or bestow)
'new-formed party therein' is the wordplay.
I cannot really see how this works, but
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is located in the answer.
'party' could be 'do' (do can informally mean a party) and 'do' is present in the answer.
This explanation may well be incorrect...
'to the' acts as a link.
Can you help me to learn more?
(Other definitions for endow that I've seen before include "Provide (with financial support, qualities etc)" , "Settle an income or property on" , "Provide capital to ensure an income for an institution" , "Woden (anag.)" , "Bequeath estate to" .)