I have component and into this component customly add tab with some functionality. Now I want that only some group of users can see that tab.
How can I add some code to give access to only group that I want?
You can try this extension to enable disable menu extension ir content for each user ir group user.
Goto this link it will helps you (https://docs.joomla.org/J2.5:Access_Control_List_Tutorial) (https://docs.joomla.org/User_Group_Access_levels_explained_in_simple_terms)