Will daily aspirin help in the reduction of blood clots in a patient with endocarditis?

Type of endocarditis. What type of endocarditis are you asking about ? Aspirin may help but typically anticoagulantion with Heparin then Coumadin (warfarin) is used to prevent embolization . Check with your cardiologist.
Probably not much. The endocarditis needs to be treated properly with antibiotics. Anticoagulant therapy is controversial but warfarin is most used.