Theatre procedure blends pearl paste with it first (3,11)
I believe the answer is:
hip replacement
'theatre procedure' is the definition.
The definition suggests a singular noun which matches the answer.
'blends pearl paste with it first' is the wordplay.
'blends' is an anagram indicator (I've seen 'blending' mean this (letters blended or mixed into a new form)).
'paste' becomes 'cement' (I can't explain this - if you can you should believe this answer much more).
'with it' becomes 'hip' (both can mean cool or fashionable).
'first' means one lot of letters go next to another.
'pearl' with letters rearranged gives 'repla'.
'repla'+'cement'='replacement'
'replacement' put after 'hip' is 'HIP REPLACEMENT'.
Can you help me to learn more?
(Other definitions for hip replacement that I've seen before include "Joint operation" , "Inserted joint" .)