Another approach, if you know eg. that DU->UP, EA->UN and AC->CO, is to feed the the whole string 'TheBardsCoupling' into wordsmith advance anagram solver, specifying say a max of 3 or 4 words output. You can scroll through every single anagram, but usually some catch the eye, for example beginning with BACON, DUPLE...(I don't know yet whether this is correct - so don't spend too much time if it doesn't seem to work...)
Can anyone explain the wordplay for 21A. I assume the entry is GALRAVAGE, or perhaps GILRAVAGE.