It looks like a wooly worm with a scrawny tail. It should not be too hard to replicate.
I suggest it is on a Mustad 3906B hook because the hook shank looks a little longer than 2x the gap. It seems to be a three part fly.
Tail - can’t tell the material, might be wool or floss, red or brown, tie this in first - at the bend.
Hackle - looks like Indian cock neck - brown - tie this in next - at the bend.
Can’t tell about the body - could be peacock herl (4 or 5 strands) or could be black chenille. Tie this in last - at the bend
Wrap chenille/peacock forward to eye - tie off
Wrap hackle to eye - tie off.
looks like a brown hackled wooley worm with a peacock herl body and haackle fiber tail. if not peacock herl then chenille. hard to tell about the body in that pic. real simple fly.
I bought one just like that on a size 12 last summer on eBay. Wes pretty well got it right. Red calf hair tail, peacock hurl body, and a brown hackle. Worked great.