British have stocked fuel near Dover, basically, to distill (4,4)

'distill' is the definition.

'british have stocked fuel near dover basically' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'have' becomes 'own' (synonyms).
'stocked' means one lot of letters goes inside another.
'fuel near' becomes 'oil' (I've seen this before. I am not sure about the 'near' bit.).
'basically' indicates taking the first letters (the first letter could be its root or base).
The initial letter of 'dover' is 'd'.
'b'+'own'='bown'
'oil'+'d'='oild'
'bown' going around 'oild' is 'BOIL DOWN'.

'to' is the link.