at a pinch

at a pinch {UK} AND in a pinch{US} (in a difficult or urgent situation) — когда прижмет, в трудной ситуации;

Example 1: He's the kind of friend you caould always turn to at a pinch. — Он тот самый друг, к которому всегда можно обратиться, когда прижмет.

Example 2:

Example 3:

see also
[when the chips are down]
[push comes to shove]
[crunch time]