A little secret initially significant (10)
I believe the answer is:
smattering
'a little' is the definition.
(I know that little can be written as smattering)
'secret initially significant' is the wordplay.
'initially' suggests taking the first letters.
'significant' becomes 'mattering' (to matter is to be significant).
The initial letter of 'secret' is 's'.
's'+'mattering'='SMATTERING'
(Other definitions for smattering that I've seen before include "superficial knowledge" , "Dash" , "bit of learning" , "Taste" , "Hint" .)