Holiday on far side of Moon? It makes a change (6)
I believe the answer is:
leaven
'it makes a change' is the definition.
(leaven can mean something that causes a change)
'holiday on far side of moon?' is the wordplay.
'holiday' becomes 'leave' (I've seen this before).
'on' means one lot of letters go next to another.
'far side of' says to take the final letters.
The last letter of 'moon' is 'n'.
'leave'+'n'='LEAVEN'
(Other definitions for leaven that I've seen before include "work" , "Add yeast to" , "Substance added to dough to make it rise" , "It makes dough rise" , "Substance that produces fermentation in dough" .)