... certain this compiler keeps pressure highest (7)
I believe the answer is:
supreme
'highest' is the definition.
(I've seen this in another clue)
'certain this compiler keeps pressure' is the wordplay.
'certain' becomes 'sure' (synonyms).
'this compiler' becomes 'me' (the person who is writing these clues).
'keeps' means one lot of letters goes inside another (inserted letters are kept inside).
'pressure' becomes 'p' (abbreviation).
'sure'+'me'='sureme'
'sureme' placed around 'p' is 'SUPREME'.
(Other definitions for supreme that I've seen before include "Unsurpassed" , "Sovereign" , "over the top" , "Unrivalled" , "topmost level" .)