Tense pressure applied to soldiers in focus of operations (7)
I believe the answer is:
theatre
'focus of operations' is the definition.
(location for surgical operations)
'tense pressure applied to soldiers' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'pressure' becomes 'heat' (I've seen this before).
'applied to' means one lot of letters go next to another.
'soldiers' becomes 're' (Royal Engineers).
't'+'heat'+'re'='THEATRE'
'in' acts as a link.
(Other definitions for theatre that I've seen before include "natural land formation?" , "Location for plays and operations" , "Drama in general" , "Play venue" , "Place for stage works" .)