This uses charade - multiple word parts are joined together in sequence to form the answer.
Start with a word for 'flyer' (think of what enables flight), then work with 'imperfect tenses' where 'imperfect' suggests an anagram of 'tenses' combined with other letters from the wordplay portion.
Answer: FEATHER ONES NEST | FEATHER (flyer/enables flight) + ONES NEST (anagram of 'tenses' + 'one' from the wordplay, with 'imperfect' as anagram indicator)