13a Stubborn Native American chicken moving about to end (5) ?ON*A
14d Be sorry for long lasting hour out of shape (5) ??NIC
Replacement definitions (26 words in total, either singly or consecutively in the same clue) must be removed from 19 clues before solving.
What's left is to be treated thematically in order to resolve all clashes and successfully complete the grid.
The theme title should be written beneath the grid. (3,5,3)
Chambers Dictionary is the primary reference. Two answers are found in OED. Two answers are abbreviations. One answer is in Collins