I allow small number inside in the dark (8)
I believe the answer is:
ignorant
'in the dark' is the definition.
(I've seen this before)
'i allow small number inside' is the wordplay.
'allow' becomes 'grant' (synonyms).
'small number' becomes 'no' (abbreviation; 'small' asks for an abbreviation).
'inside' means one lot of letters goes inside another.
'grant' going around 'no' is 'gnorant'.
'i'+'gnorant'='IGNORANT'
(Other definitions for ignorant that I've seen before include "Lacking knowledge or lacking manners" , "not read" , "Knowing nothing" , "Lacking in or good manners" , "blissful?" .)