A girl screwed on the head of CFL bulb (6)
I believe the answer is:
'bulb' is the definition.
(I have seen 'Pungent bulb ' mean 'garlic' so perhaps 'bulb' could also mean 'garlic')
'a girl screwed on the head of cfl' is the wordplay.
'screwed' indicates anagramming the letters.
'on' is an insertion indicator (as in clothing \'on\' a person).
'the head of' indicates taking the first letters.
The initial letter of 'cfl' is 'c'.
'girl' is an anagram of 'grli'.
'a' put within 'grli' is 'garli'.
(Other definitions for garlic that I've seen before include "Pungent-tasting bulb" , "Pungent edible bulb" , "Plant of the onion family" , "Pungent bulb - vampires hate it" , "Bulbous herb used in cooking" .)