We gel over base term for Alan Sugar (7)
I believe the answer is:
sweeten
'sugar' is the definition.
(I know that sugar is a more specific form of the action sweeten)
'we gel over base term for alan' is the wordplay.
'gel' becomes 'set' (I've seen this in another clue).
'over' indicates putting letters inside.
'base' becomes 'e' (Euler's number - base of natural logarithms).
'term for' says to take the final letters (the letter which terminates the word).
The last letter of 'alan' is 'n'.
'we' going inside 'set' is 'sweet'.
'sweet'+'e'+'n'='SWEETEN'
(Other definitions for sweeten that I've seen before include "Make fresh" , "pacify!" , "Add sugar etc" , "Make sugary or saccharine" , "temper" .)