Very briefly, I spoilt child, having got old and wobbly (7)
I believe the answer is:
vibrato
'wobbly' is the definition.
(vibrato describes a wobbly musical effect)
'very briefly i spoilt child having got old' is the wordplay.
'very briefly' becomes 'v' (abbreviation; 'briefly' indicates an abbreviation).
'spoilt child' becomes 'brat' (I've seen this before).
'having got' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'v'+'i'+'brat'+'o'='VIBRATO'
'and' acts as a link.
(Other definitions for vibrato that I've seen before include "Rapid pitch variation" , "Pulsating effect in instrumental or vocal tone" , "Singing effect" , "Rapid alternation in pitch" , "Oscillatory effect" .)