Part of sex tremendously far out (7)
I believe the answer is:
extreme
'far out' is the definition.
(I've seen this before)
'part of sex tremendously' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'EXTREME' is hidden in the letters of 'sex tremendously'.
(Other definitions for extreme that I've seen before include "Very great; not usual" , "too much" , "Of the greatest intensity" , "Uttermost" , "Furthest or highest degree of something" .)