I need a good definition of .... the phrase ... to get left in the lerch?

TO be left in the lurch means to be stood up, left behind without knowledge, to be abandoned to fend for yourself.

This is the Oxford dictionary's definition:

To be left in the lurch: to leave in adverse circumstances without assistance.

In common usuage it means if you are left in a situation other than what you intended, or to be left to cope with someone else's problem.

to be left in the lurch..............is to be left in a difficult and embarrasing position by someone or something else.