Toes somehow get hard? Not these (5)
I believe the answer is:
those
'not these' is the definition.
(I've seen this before)
'toes somehow get hard?' is the wordplay.
'somehow' indicates anagramming the letters.
'get' is an insertion indicator.
'hard?' becomes 'h' (abbreviation used in pencil classifications).
'toes' is an anagram of 'tose'.
'tose' placed around 'h' is 'THOSE'.
(Other definitions for those that I've seen before include "the more far out?" , "The (things) there" , "Nostalgic utterance" , "Plural form of that" , "Ethos (anag.)" .)