Follow tennis rules, oddly (5)
I believe the answer is:
ensue
'follow' is the definition.
(thesaurus)
'tennis rules oddly' is the wordplay.
'oddly' means one should take alternating letters.
'tennis'+'rules'='tennisrules'
The alternate letters of 'tennisrules' are 'ENSUE'.
(Other definitions for ensue that I've seen before include "Follow later" , "Proceed" , "Turn out" , "Cultivate plants/vegetables" , "Come next" .)