Reduction of personnel, in decline over long period (9)
I believe the answer is:
shrinkage
'reduction' is the definition.
(thesaurus)
'personnel in decline over long period' is the wordplay.
'personnel' becomes 'HR' (Human Resources).
'in' means one lot of letters goes inside another.
'decline over' becomes 'sink' (sinking is a kind of declining. I am not sure about the 'over' bit.).
'long period' becomes 'age' (I've seen this before).
'hr' going inside 'sink' is 'shrink'.
'shrink'+'age'='SHRINKAGE'
'of' is the link.
Can you help me to learn more?
(Other definitions for shrinkage that I've seen before include "Contraction" , "theft from store?" , "effect of melting?" , "Process of becoming smaller" , "Process by which something becomes smaller" .)