Can this be used for small area plaster wall defect ?

Thank you for posting your inquiry. While this would be possible in theory, the fact that this material set to a soft/pliable texture and is not sandable, may prove to be a challenge and/or may not produce a cosmetically acceptable result. At your convenience, please contact DAP’s Technical Customer Service Department at 888-327-8477 so that we can obtain some additional information from you and discuss some product options with you.