One ''spiky'' type to go off the deep end, rambling (9)
I believe the answer is:
itinerant
'rambling' is the definition.
(I've seen this before)
'one 'spiky' type to go off the deep end' is the wordplay.
I cannot quite see how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
This explanation may well be incorrect...
(Other definitions for itinerant that I've seen before include "Nomadic" , "Travelling from place to place" , "Wandering from place to place" , "(Person) on the move" , "Person who moves from place to place" .)