What can control large tour going round? (9)
I believe the answer is:
regulator
'what can control' is the definition.
'large tour going round?' is the wordplay.
'going round?' is an anagram indicator.
'large'+'tour'='largetour'
'largetour' anagrammed gives 'REGULATOR'.
(Other definitions for regulator that I've seen before include "Such as OFGAS, OFTEL etc" , "Governor" , "source of rules?" , "Supervisor" , "Ofsted perhaps" .)