Travel slowly along the ground, in a cab, say? (4)
I believe the answer is:
taxi
'travel slowly' is the definition.
(synonyms)
'along the ground in a cab say?' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'a' is found in the answer.
The remaining letters 'xi' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for taxi that I've seen before include "Cab for hire" , "(Plane) roll over tarmac" , "Prepare to fly" , "Hired vehicle" , "use apron" .)