The definition of the second clue in 1a is 'waves' - big ones. The wordplay should click once you've got the solution.
In 1d, as in 10d, 'filler' refers to the entity filling the hole, so you're looking for an adjective that describes the 'filler'.
I've been doing this pretty much in spite of the instructions, rather than with them: "entered left to right in other spaces left vacant" seems gibberish to me. Perhaps "in" is meant to be "and"? Anyhow, I plough on.