Tackled dominant doctrines, initially slippery like IT giant’s caveat? (5,3,10,5)

'tackled dominant doctrines initially slippery' is the definition.
I can't tell whether this defines the answer.

'like it giant's caveat?' is the wordplay.
I cannot quite understand how this works, but
'like' could be 'ly' (similar in meaning) and 'ly' is located in the answer.
'it' could be 'sa' (old-fashioned abbreviation for sex appeal) and 'sa' is located in the answer.
'caveat?' could be 'condition' (I've seen this in another clue) and 'condition' is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?