And the youngster, who had a spell as a teenager with French club Clermont Auvergne, says he's looking forward to the challenge.
"I went through a tough pre-season with the club and it's great to get rewarded with this chance to show what I can do," said McAndrew.
"I had a good season with Melrose last year and trained the whole of this pre-season with Edinburgh, as the club needed scrum-half cover.
"Moving to France at a relatively young age was fairly daunting, but it was an excellent opportunity to develop my skills there at a time when Nathan Hines, Jason White and Mark Bennett were also involved with the club.
"Then I got the opportunity to return to Scotland and was able to get more game time last season at Melrose."
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