Lack of approval for crevices (5)
I believe the answer is:
nooks
'for crevices' is the definition.
(I've seen this in another clue)
'lack of approval' is the wordplay.
'lack of' becomes 'no' (lack of money is no money).
'approval' becomes 'oks' (I can't explain this - if you can you should believe this answer much more).
'no'+'oks'='NOOKS'
Can you help me to learn more?
(Other definitions for nooks that I've seen before include "out-of-the-way places" , "Secluded retreats" , "secluded parts" , "In security areas" , "Sheltered corners" .)