"Synonyms for serious" not recognised as a correct answer - need to add some alternative possible keywords that successful solvers might use. Also, two rows of synonyms and two of wordplay - might be better to vary the types of connection.

Bit odd to accept synonyms for one group and not the other, it's really the best term to accept that doesn't require players to psychically know what you are thinking wording-wise. I agree that a bit of variation in connections would help too.

From a grammar pov, line 1 'intensifier' and line 2 'gerund' .