Strain to lift off with about a ton inside (8)

'strain' is the definition.
(synonyms)

'lift off with about a ton inside' is the wordplay.
'off' indicates anagramming the letters.
'with' says to put letters next to each other.
'about' says the letters should be written in reverse.
'ton' becomes 'etr' (I can't explain this - if you can you should give a lot more credence to this answer).
'inside' indicates putting letters inside.
'a' going inside 'etr' is 'etar'.
'etar' reversed gives 'rate'.
'lift' anagrammed gives 'filt'.
'filt'+'rate'='FILTRATE'

'to' is the link.

Can you help me to learn more?