Harrow teacher cycling to Thailand (7)
I believe the answer is:
torment
'harrow' is the definition.
(thesaurus)
'teacher cycling to thailand' is the wordplay.
I cannot really see how this works, but
'to' is found in the answer.
'thailand' could be 't' (abbreviation on car registration plates) and 't' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for torment that I've seen before include "Punish" , "Pester or tease unmercifully" , "Persecute" , "Cause great pain to" , "Extreme mental or physical distress" .)