Fake head of personnel rings cleaner (7)
I believe the answer is:
shampoo
'cleaner' is the definition.
(shampoo cleans hair)
'fake head of personnel rings' is the wordplay.
'fake' becomes 'sham' (sham can mean fake or pretend).
'head of' says to take the initial letters.
'rings' becomes 'oo' (two O's - O resembles a ring).
The initial letter of 'personnel' is 'p'.
'sham'+'p'+'oo'='SHAMPOO'
(Other definitions for shampoo that I've seen before include "treat shock?" , "Hair-cleaning product" , "Hair-cleaner" , "Soapy liquid for hair" , "clean" .)