Tendency to be nosy about uninhibited model (10)
I believe the answer is:
propensity
'tendency' is the definition.
(I know that tendency can be written as propensity)
'be nosy about uninhibited model' is the wordplay.
'be nosy' becomes 'pry' (to pry is to investigate nosily).
'about' is an insertion indicator.
'uninhibited' becomes 'open' (I've seen this in another clue).
'model' becomes 'sit' (e.g. for a painting).
'open'+'sit'='opensit'
'pry' enclosing 'opensit' is 'PROPENSITY'.
'to' acts as a link.
(Other definitions for propensity that I've seen before include "Bent" , "Inclination; tendency" .)