There may be a misprint in the definition.
The clue may be normal or the answer shorter than length indicated.
12 Foes endlessly push on, taking Italy in silence (8)
45 Former Secretary to the Admiralty ignores variable savings schemes (8)
19d Stones through walls: standard defence positions (9)
Thanks NAC.
Still don't know what the theme is.
Also how to modify the answers. 9d turns into an island.
But the others are not as clear.
These 3 answers should help.
12d Loco part made in China (4) P??T
3d Third of fish increased twenty-fold in streams (4) EE??
41d Non-perjorative term for fellow American cop (4) ?O?A