Power engineers are inclined to put on an act (7)
I believe the answer is:
pretend
'an act' is the definition.
(I know that act can be written as pretend)
'power engineers are inclined to put on' is the wordplay.
'power' becomes 'p' (symbol in physics).
'engineers' becomes 're' (abbreviation for Royal Engineers).
'are inclined to' becomes 'tend' (eg 'they tend to go to bed early').
'put on' says to put letters next to each other (some letters go on or after others).
'p'+'re'+'tend'='PRETEND'
(Other definitions for pretend that I've seen before include "Behave unnaturally" , "Dissemble" , "make a false claim" , "bluff" , "Simulated" .)