Robust redhead enters room (6)
I believe the answer is:
sturdy
'robust' is the definition.
(similar in meaning)
'redhead enters room' is the wordplay.
I cannot really understand how this works, but
'redhead' could be 'r' (the head letter of red) and 'r' is present in the answer.
'room' could be 'study' (study is a kind of room) and 'study' is found in the leftover letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sturdy that I've seen before include "Strong, solid" , "Strong and sturdily built" , "Rugged" , "Well-constructed" , "Stalwart, stout, tough" .)