This term is usually used for an ENG INOP situation, where if not already at MCT then one should level off to accelerate, clean up to Flap Zero (clean) and be able to achieve the final climb (Green DOT for Airbus speak) where MCT can be selected all within the TOGA time limitation (usually 10 mins).
In general terms it is approx 1000' above the minimum acceleration ALT unless operating from hight altitude airports.
