Female, feeble soul initially, burns brightly (6)
I believe the answer is:
flames
'burns brightly' is the definition.
(burns with flames)
'female feeble soul initially' is the wordplay.
'female' becomes 'f' (abbreviation).
'feeble' becomes 'lame' (lame can mean feeble or pathetic).
'initially' suggests taking the first letters.
The initial letter of 'soul' is 's'.
'f'+'lame'+'s'='FLAMES'
(Other definitions for flames that I've seen before include "Blazes, flares" , "exes!" , "Glowing bodies of ignited gas generated by fire" , "Hot glows from the fire" , "Insulting emails" .)