Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
con-cesso, āvi, 1, v. a., to cease, leave off, desist (ante- and post-class., and very rare): lavari aut fricari, Plaut. Poen. 1, 2, 9: quid ego hic properans concesso pedibus, linguā largior? id. As. 2, 2, 24; Front. Ep. ad M. Antonin. Aug. 1, 2.
Of things as subjects: concessavit praeceptum, Tert. Fug. Pers. 6.