Sometimes a clause like the one Marjorie references will appear as
"assist with regulatory matters".  There are potential conflicts of
interest if the researcher is affiliated with the company, but these
conflicts should be handled at the university.  From what the doctors
used to tell me, this is not unusual.  The key is to be paid for the
time and effort involved.  It is also important to restrict the use of
the university's and researcher's names in marketing.  In my mind, I
associate this activity with that of the filing of patent applications...
our researchers are often asked to "assist with patent filings."
I am also assuming that your researcher will be an "expert witness" and not
the primary person advocating in front of the FDA.