Turn about, as a cross-country runner (3)
I believe the answer is:
ure
'a cross-country runner' is the definition.
'ure' can be an answer for 'runner' (river in Yorkshire). I'm unsure of the 'a cross-country' bit.
'turn about' is the wordplay.
'turn' becomes 'u' (a 'U-turn' is a kind of turn).
'about' becomes 're' ('re' means regarding or about).
'u'+'re'='URE'
'as' is the link.
Can you help me to learn more?
(Other definitions for ure that I've seen before include "Wensleydale river" , "North Yorkshire river" , "River of N. Yorkshire" , "Midge --, singer" , "Ripon's river" .)