Huge resistance after one picked up tailless rodent (8)
I believe the answer is:
enormous
'huge' is the definition.
(synonyms)
'resistance after one picked up tailless rodent' is the wordplay.
'resistance' becomes 'r' (electronics abbreviation).
'after' is a charade indicator (letters next to each other).
'picked up' says the letters should be written backwards.
'tailless' means to remove the last letter (the tail of the word is removed).
'rodent' becomes 'mouse' (mouse is a kind of rodent).
'one' backwards is 'eno'.
'mouse' with its final letter taken off is 'mous'.
'r' put after 'eno' is 'enor'.
'enor'+'mous'='ENORMOUS'
(Other definitions for enormous that I've seen before include "'Huge, gigantic (8)'" , "Colossal, huge" , "Immense" , "Mammoth" , "Vast" .)