Precocious child supported by family in outskirts of Watford (10)
I believe the answer is:
wunderkind
'precocious child' is the definition.
(term for a talented child)
'supported by family in outskirts of watford' is the wordplay.
'supported by' becomes 'under' (eg being under someone's guidance).
'family' becomes 'kin' (synonyms).
'in' is an insertion indicator.
'outskirts of' says to hollow out the word (remove centre letters).
'watford' with its middle removed is 'wd'.
'under'+'kin'='underkin'
'underkin' put into 'wd' is 'WUNDERKIND'.
(Other definitions for wunderkind that I've seen before include "Extraordinary issue" , "One having early success" , "Child prodigy" , "Clever young person" , "Perhaps Mozart" .)