Little goldfinch regularly guarded by parent (7)
I believe the answer is:
modicum
'little' is the definition.
(thesaurus)
'goldfinch regularly guarded by parent' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'guarded by' indicates putting letters inside.
'parent' becomes 'mum' (mum is a kind of parent).
The alternate letters of 'goldfinch' are 'odic'.
'odic' placed into 'mum' is 'MODICUM'.
(Other definitions for modicum that I've seen before include "Token amount" , "touch" , "Little bit" , "I cod Mum into providing a small quantity" , "Moderate quantity" .)