If you right click on the item in the study feature tree you might see a suitable option.
rmb > exclude will remove it completely, the restraints won't transfer
rmb > rigid will keep it, but it will act like a solid block
it sounds like you need the cylinder if you need to restrain it to get the deformation to be correct. making it rigid or moving the restraint to where the cylinder connects to the rest might stiffen it up even more. can you post a picture so we can take a look at whether theere is a better method?
You shall consider remote load/ displacement in you situation as restrain ... Place coordinate system within cylider center with one of axis cooncident to cylinder axis.... as reference for remote load /displacement and set 0 values for correspondind degrees of freedom.
It will simulate your restrains and reduce calculation error for matrix that will ommit non interesting finite elements elasticity.
Good luck / one beer 4 me ;)