Easiest for some time - an under 2-hour job. But still unhappy about the central 3-letter. I see what it has to be but is it really a word? My Chambers is in another country ....
Also found it considerably more straightforward than last week. I would be interested to know which clue caused the penny to drop on the theme - for me it was "Bug causing ruin..."
One to go: 'American president's etc...'. I've got _R_E_A as the crossers and an answer that feels right, but I can't for the life of me see the parsing.