Guess Walcott gets increase (8)
I believe the answer is:
theorise
'guess' is the definition.
('guess'->'theorize' is in my internal thesaurus and 'ize'->'ise')
'walcott gets increase' is the wordplay.
'walcott' becomes 'Theo' (footballer Theo Walcott).
'gets' says to put letters next to each other.
'increase' becomes 'rise' (rising is a kind of increasing).
'theo'+'rise'='THEORISE'
(Other definitions for theorise that I've seen before include "Conjecture, hypothesise" , "Think up possible explanations" , "Speculate by reasoning" , "Form view" , "Express ideas" .)