Capable of being stretched in future possibly to include the centre of Basildon (7)
I believe the answer is:
tensile
'capable of being stretched' is the definition.
(I've seen this before)
'future possibly to include the centre of basildon' is the wordplay.
'future possibly' becomes 'tense' (future is a kind of tense).
'to include' means one lot of letters goes inside another.
'the centre of' says to take the centre.
The middle letters of 'basildon' are 'il'.
'tense' enclosing 'il' is 'TENSILE'.
'in' acts as a link.
(Other definitions for tensile that I've seen before include "Capable of being stretched, kind of strength" , "Capable of stretching" , "Relating to stretching" , "Able to be stretched" , "Relating to stress" .)