A pharmacokinetic interaction with ostarine which would hinder elimination of amoxicillin or the clavulanate would be the major problem of the combination- however this would seem highly unlikely given ostarines primary eliminated route is (unchanged) via feces, contrasting amoxicillin/clavulanate primary kidney elimination route.
The pharmacokinetic data on ostarine doesn't define the metabolism/excretion of the biotransformed metabolites. Although these metabolites account for only a small proportion of the whole dose- there is a very narrow scope for potential interaction which can't be predicted in the absence of this data. If, on a very unfortunate chance, this were the case, it would most likely manifest, as do most mild penicillin-based reactions, as a red bumpy rash.