I think I have an incorrect answer thowing off the whole corner but here are the clues and what I have (bear in mind one or more of the letters might be off!)
2d Board a rail service E?T???N
3d Pompously Moralising S?N???T???S
4d Calculate R?C???
16a Duenna F???????O
Given I have a problem with 2-4d the first letters I have could be wrong. I have 'overstretched' as an answer to 'too extended'
Ta.