A fling with almost entirely inflexible, unscrupulous lawyer (7)
I believe the answer is:
shyster
'unscrupulous lawyer' is the definition.
(I've seen this before)
'a fling with almost entirely inflexible' is the wordplay.
'a fling' becomes 'shy' (I've seen this in other clues).
'with' means one lot of letters go next to another.
'almost entirely' means to remove the last letter.
'inflexible' becomes 'stern' (similar in meaning).
'stern' with its final letter taken away is 'ster'.
'shy'+'ster'='SHYSTER'
(Other definitions for shyster that I've seen before include "Wheeler-dealer" , "Informally, an unscrupulous or unprofessional person - sounds bashful?" , "Lawyer using unethical methods" , "Unscrupulous or disreputable person" , "Pettifogger" .)