Question Author
Many thanks to all you kind ABers who have tried to help me with this one so far (smouse, boxtops, mamyalynne, EGTB, mazie).
It is very frustrating that the answer must begin or end with an 'i, as both the 'change' and 'over' suggestions were good. (Unfortunately, the quiz has a hidden sequence of European countries made from the either the first or last letter of the answer word, and if I'm right, this should be 'i', so our answer should begin or end with 'i'.
Looks like 'inter par' might be an abbreviation of the Latin phrase suggested by Mazie, so in the absence of a moment of genius from myself between now and posting of the quiz (v.unlikely), I'll probably stick with 'inter'.
Still think there is a possibility that the 'par' bit of the clue might be a mistake though ....