Going underground, Louis XIV saving skin, almost (10)

'going underground' is the definition.
The definition suggests a present participle verb which matches the answer.

'louis xiv saving skin almost' is the wordplay.
'louis xiv' becomes 'sun king' (Louis XIV was nicknamed the Sun King).
'saving' indicates putting letters inside.
'skin' becomes 'pelt' (an animal's skin).
'almost' means to remove the last letter (most of the word but not all of it).
'pelt' with its last letter taken away is 'pel'.
'sunking' placed around 'pel' is 'SPELUNKING'.

Can you help me to learn more?