what kind of glue?
a drycleaner should be able to get it out unless its super glue, ive never been able to get that stuff to even soften up
but white glue, "hot" glue or model plane glue can be removed. if you want to put some acetone on it in a place you cant see to check for colorfastness and to make sure it wont destroy the garment it would be a good idea, could also try glue solvent from a hoby shop if you can get any.
then acetone on part of a rag held over it for a while to soften the glue, then peel it gently off
glue on jeans shouldnt be a problem for a drycleaner, glue on a sweater can be a bitch though