Boxer defending position completely still (4-6)
I believe the answer is:
rock-steady
'completely still' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'boxer defending position' is the wordplay.
'boxer' becomes 'rocky' (boxer in the Rocky films).
'defending' means one lot of letters goes inside another (inserted letters are defended).
'position' becomes 'stead' (synonyms).
'rocky' going around 'stead' is 'ROCK-STEADY'.
Can you help me to learn more?
(Other definitions for rock-steady that I've seen before include "Absolutely stable" , "Never deviating" .)