Decoration for the head of diminutive fellow? (7)
I believe the answer is:
chaplet
This clue might be a double definition.
'decoration for the head' is the first definition.
(garland worn on the head)
'diminutive fellow?' is the second definition.
'chaplet' can be an answer for 'fellow?' (I have seen 'Little fellow' mean 'chaplet' so perhaps 'fellow' could also mean 'chaplet'). I'm not sure about the 'diminutive' bit.
'of' is the link.
(Other definitions for chaplet that I've seen before include "Garland or wreath for the head" , "flower arrangement" , "Little fellow" , "Circular garland for the head" , "top band?" .)