Here's Longman's self-serving definition:
What's
a production dictionary?
A
production dictionary guides you to exactly the right
word you need for the context. Let's say you're writing
an essay about how you spent your weekend. You had
a "good" time: you went to a "good"
party, the film you saw was "good" and the
meal in the restaurant was "good". You've
used the word "good" three times; wouldn't
it have been better if you could have used some different
words with similar and more appropriate meanings -
if only you'd known how to find them?
This
is when a production dictionary is needed. You could
have looked up the word "good", and realised
that actually you went to a "brilliant" party,
the film you saw was "excellent" and the meal
in the restaurant was "fantastic"! It's that
easy, because when you look up a word in a production
dictionary, you'll find lots of related words in the
same section, so you can find exactly what you're looking
for straightaway.
Ever means at any time-- it's a kind of post-modifying intensifier for
first, I think