I think that's right
the clue being step-up generator (11)
a parent being a generator of children ( think of the trem generations)
a grandparent being a step up from that.
p.s. in future best put the clue in the question with known letters and ?'s for missing letters as not everyone on this site will have the crossword you refer to. As it happedn I filled that partcilar one in a few days agoi.