As Barretter indicates each group of three clues has a definition (mostly single word but some are two or three) either preceded by or followed by a letter mixture (ie an anagram) of the answer. Once you have a few answers entered you can then start looking for the letter mixtures since you'll know some of the letters (helps if you have some of the first letters of the answers).
I started with 21a and 18d and got most of the bottom left corner fairly quickly, followed by the top left corner. The rest gradually fell into place though I did have some difficulty getting into the top right corner.
If you need any further help or want to check any answers do get back.