I have this sentence in one of my N1 practice books, but I am not really sure how to translate this one:
げっそり translate to 'being disheartened' - how to translate げっそり自由
"Since I was laid off owing to the recession, I have decided to enjoy my freedom ~~~~ly for a while."
There are dozens of words in Japanese that take the form of 「〇っ〇り」 (second kana is the small っ). Over 95% of those are adverbs and many have an onomatopoeic quality to them.
A few 〇っ〇り-words could certainly be used to fill in the blank in the sentence above, but unfortunately, 「げっそり」 is not one of them even if your book said it was.
「げっそり」 means "dejectedly", "disheartenedly", etc. It just does not go well with the verb 「楽しむ」 = "to enjoy". That is, unless this is supposed to be some kind of a joke.
The possible 〇っ〇り-words would include 「ゆっくり」 (leisurely)、「ひっそり」 (quietly) 、「しっかり」 (surely), etc.