Crack very visible in bottom of shoe (5)
I believe the answer is:
solve
'crack' is the definition.
(thesaurus)
'very visible in bottom of shoe' is the wordplay.
'very' becomes 'v' (abbreviation).
'visible in' means one lot of letters goes inside another.
'bottom of shoe' becomes 'sole'.
'v' put inside 'sole' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Find the answer to this clue, for instance" , "as you're trying to do now" , "Clear up a mystery" , "Find the key - work out" , "Work out answer to puzzle" .)