Drive from centre of Thurso, say, northwards (4)
I believe the answer is:
urge
'drive' is the definition.
(I've seen this before)
'centre of thurso say northwards' is the wordplay.
'centre of' says to take the centre.
'say' becomes 'eg' (both can mean for example).
'northwards' says the letters should be written in reverse (in a down clue, letters go up or 'north').
The middle letters of 'thurso' are 'ur'.
'eg' in reverse letter order is 'ge'.
'ur'+'ge'='URGE'
'from' is the link.
(Other definitions for urge that I've seen before include "Sudden desire" , "Egg on, encourage to proceed" , "Encourage, press" , "Encourage or entreat earnestly" , "Press (persistently)" .)