Local crossword, cryptic. Please can you help?

[tarasmum]

17a As principal countries, they are geographically outstanding. (9) - E - D - T - - -
21a Iraqi port from which Arabs come (5) - A - R -
2d Make a trench - the tree won't grow without it (3) - A -
16d Capital beginning of Othello - one of Shakespeare's leading characters (5) - O -E -

Thanks in anticipation, Tarasmum.

[tarasmum]

Hi, Think the answer to 21a is Basra (anagram of arabs). Tarasmum

[bibblebub]

17a headlands ? if the T is wrong

16d Rome O

[bibblebub]

2d sap

[tarasmum]

thanks so much bibblebub, I like these answers. Now i need help with the answer I have changed please.
13d A part's recast as an eastern tyrant (6) S - A - A -
I originally had Sparta but that was obviously wrong. Please can you help?
By the way, I have figured out 2d SAP
Thanks in anticipation - Tarasmum

[bibblebub]

satrap http://dictionary.ref...p?r=75&src=ref&ch=dic

[tarasmum]

Bibblebub, you are a genius! Thank you!
Tarasmum

[bibblebub]

you're very welcome

[tarasmum]

Have a great weekend!