... adapting pine bed's nails to make key (13)
I believe the answer is:
indispensable
'key' is the definition.
(thesaurus)
'adapting pine bed's nails' is the wordplay.
'adapting' indicates an anagram.
'pine'+'beds'+'nails'='pinebedsnails'
'pinebedsnails' anagrammed gives 'INDISPENSABLE'.
'to make' is the link.
(Other definitions for indispensable that I've seen before include "Absolutely necessary" , "Vitally necessary" , "Essential" .)