Size of certain chaps in flesh (11)
I believe the answer is:
measurement
'size' is the definition.
(I've seen this before)
'certain chaps in flesh' is the wordplay.
'certain' becomes 'sure' (similar in meaning).
'chaps' becomes 'men' (I've seen this before).
'in' means one lot of letters goes inside another.
'flesh' becomes 'meat' (I have seen 'Edible flesh' mean 'meat' so perhaps 'flesh' could also mean 'meat').
'sure'+'men'='suremen'
'suremen' inserted inside 'meat' is 'MEASUREMENT'.
'of' is the link.
(Other definitions for measurement that I've seen before include "Mensuration" , "What a ruler may give" , "Dimension" , "Size" .)