Exercise tiring when starting late (8)
I believe the answer is:
training
'starting late' is the definition.
The definition and answer can be both to do with motion as well as being present participle verbs.
Maybe you can see an association between them that I can't see?
'exercise tiring' is the wordplay.
'exercise' becomes 'train' (training is a kind of exercising).
'tiring' becomes 'ing' (I can't justify this - if you can you should give a lot more credence to this answer).
'train'+'ing'='TRAINING'
'when' is the link.
Can you help me to learn more?
(Other definitions for training that I've seen before include "Instructing, teaching" , "Tuition" , "Working out" , "Learning a skill" , "Regime" .)