The answer to the clue for 1a (7 letters) becomes the final thematic (down) entry.
The wordplay is - 'productive'/abundant (4 letters) + 'period' (4 letters, but minus the last one).
The answer to 3 is entered at 1a - someone famous for farces - full name but 'gutted',
For 2d - change the name, the 'old Dutch' is his very famous wife.