One party has a grip on my part of America (5)
I believe the answer is:
idaho
'my part of america' is the definition.
I can't tell whether this defines the answer.
'one party has a grip' is the wordplay.
'one' becomes 'i' (Roman numeral).
'party' becomes 'do' (do is a kind of party).
'has' is an insertion indicator.
'a grip' becomes 'ah' (I can't explain this - if you can you should believe this answer much more).
'do' placed around 'ah' is 'daho'.
'i'+'daho'='IDAHO'
'on' is the link.
Can you help me to learn more?
(Other definitions for idaho that I've seen before include "US state, capital Boise" , "O, I had a change in this state" , "US state S. of Montana" , "North-western US state" , "My Own Private -- (1991 film)" .)