Sentence:  When the issue is a political one, reporters tend to watch for the reactions of certain “<WSD>bell cow</WSD>” journalists. 
Meaning of the word marked with <WSD> tags:  A leader; an influencer<ref>W. Davis Folsom, "Understanding American Business Jargon: A Dictionary", Westport, Connecticut: Greenwood Press, 2nd edition, 2005, p. 27.[https://archive.org/details/understandingame00wdav]</ref>.