The highlighted words all contain the three letter word WIN in that order. This indicates that the buyers are looking for sets containing the same three letter word spelled out within each word of the set.
The nine sets can be sold as follows:
BAR: bargain / baroque / barrier / cabaret / crowbar / embargo / rhubarb
DEN: broaden / denizen / evident / maidens / prudent / rodents / student
CAT: catalog / caterer / copycat / educate / polecat / scatter / wildcat
IRE: acquire / esquire / fairest / firefly / heiress / inquire . require
EAR: clearly / earnest / fearful / forearm / midyear / tearoom / unearth
FIN: confine / finally / finance / finicky / griffin / muffins / roofing
HER: butcher / cherish / fishery /heretic / inherit / nowhere / therapy /
AGE : average / cabbage / eagerly / manager / pageant / tragedy / village
GAL: fugally / gallant / gallery / gallows / illegal / legally/ / regally
