At moderator's request, I've been asked to limit the number of batched clues to a maximum of four. Also, I've been reminded to thank all those who help me out - I think I forgot once and they pulled me up on it. Cheers & here are the clues:
13a. Having terror of hard study with a blank crossword to fill in
HAG-RIDDEN
16a. See one's sunk in a depression for most of December
ADVENT
20a. Most nervous about running into cliff in cutter
SCIMITAR
23a. Sort of ant that likes to work a good deal?
CARPENTER
Parses for the above please.