Intense old flame very short with Hoskins (7)
I believe the answer is:
extreme
'intense' is the definition.
(similar in meaning)
'old flame very short with hoskins' is the wordplay.
'old flame' becomes 'ex' (an ex-lover).
'very' becomes 'tres' ('very' in French).
'short' means to remove the last letter.
'with' means one lot of letters go next to another.
'hoskins' becomes 'me' (where the crossword setter is 'Hoskins').
'tres' with its last letter taken away is 'tre'.
'ex'+'tre'+'me'='EXTREME'
(Other definitions for extreme that I've seen before include "Exceptional - maximum - farthest" , "Very serious" , "Going to great lengths" , "Immoderate" , "Most remote or utmost" .)