Flannel cost personnel silver (7)
I believe the answer is:
washrag
'flannel' is the definition.
(I know that flannel can be written as washrag)
'cost personnel silver' is the wordplay.
'cost' becomes 'was' (I can't justify this - if you can you should believe this answer much more).
'personnel' becomes 'hr' (Human Resources).
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'was'+'hr'+'ag'='WASHRAG'
Can you help me to learn more?
(Another definition for washrag that I've seen is " American means to clean mug".)