These four friends always act clannishly, and don't let us participate in their activities.    From Wordnet, Princeton University. 

Adjective : the clannish behavior of the original members of the country club.    From Dictionary.com. 

Often though she might scarify him with her sharp tongue, she was genuinely attached to him, and her clannishly hospitable soul would have been sorely wounded if he had not spent a few days at Trevarthen Wood while he was in the neighbourhood.    From Wordnik.com.  [The Moon out of Reach] Reference

He loved his family clannishly, and he was rejoiced that they were all again near to him.    From Wordnik.com.  [Further Chronicles of Avonlea] Reference

Family were accustomed to living clannishly, even on roundup, and only when they tacitly adopted a man, as they had adopted Pink and Irish and, last but not least important, Andy Green, did they take note of that man's mood and demand reasons for any surliness.    From Wordnik.com.  [The Happy Family] Reference

2001) for one, and more domestic, or at least more recognizably realistic (but Gordon's always been realistic; he pretty much captured the tone and texture of pre-med campus life in Re-Animator, of clannishly unfriendly small coastal towns in Dagon) fare like the low-key.    From Wordnik.com.  [Critic After Dark] Reference