About to observe power throttling source of liberty? Don’t get aroused (9)
I believe the answer is:
oversleep
'don't get aroused' is the definition.
'about to observe power throttling source of liberty?' is the wordplay.
'about' becomes 'over' (I've seen this before**).
'to observe' becomes 'see' (I've seen this before).
'power' becomes 'p'.
'throttling' means one lot of letters goes inside another.
'source of' indicates taking the first letters.
The first letter of 'liberty' is 'l'.
'see'+'p'='seep'
'seep' enclosing 'l' is 'sleep'.
'over'+'sleep'='OVERSLEEP'
(Other definitions for oversleep that I've seen before include "start being late?" , "Wake too late" , "show signs of exhaustion?" , "Get up too late" , "Fail to hear alarm clock?" .)