Keep informed of tiny changes (6)
I believe the answer is:
notify
'keep informed' is the definition.
(to notify someone is to keep them informed)
'of tiny changes' is the wordplay.
'changes' indicates anagramming the letters.
'of'+'tiny'='oftiny'
'oftiny' anagrammed gives 'NOTIFY'.
(Other definitions for notify that I've seen before include "Declare" , "Make known" , "Formally tell" , "Formally inform" , "Formally advise" .)