Woman driven off a cliff when steering mechanism breaks cheers (6)
I believe the answer is:
thelma
'woman' is the definition.
'mechanism breaks cheers' is the wordplay.
'mechanism' becomes 'helm' (helm is a kind of mechanism).
'breaks' means one lot of letters goes inside another (inserted letters break into the word).
'cheers' becomes 'ta' (both can informally mean thank you).
'helm' placed within 'ta' is 'THELMA'.
'driven off a cliff when steering' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for thelma that I've seen before include "Girl" , "Louise's partner" , "Louise's friend" , "Woman" , "Foreign policy of force" .)