20d is HYPHEN - hyen(a) around PH and the 'definition' is an example
16a is DEEJAYS - Dee + jays
Grouchy does have a point, though - I managed to remember what the answers were, but don't assume that anybody answering will actually have done the puzzle
And if this was an early attempt at a Grauniad puzzle, don't be put off - this was a particularly awkward one and personally I was unhappy with quite a number of the clues